chore(oidc): remove legacy storage methods (#10061)

# Which Problems Are Solved

Stabilize the optimized introspection code and cleanup unused code.

# How the Problems Are Solved

- `oidc_legacy_introspection` feature flag is removed and reserved.
- `OPStorage` which are no longer needed have their bodies removed.
- The method definitions need to remain in place so the interface
remains implemented.
  - A panic is thrown in case any such method is still called

# Additional Changes

- A number of `OPStorage` methods related to token creation were already
unused. These are also cleaned up.

# Additional Context

- Closes #10027 
- #7822

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

proto/zitadel/feature/v2/instance.proto

@@ -11,8 +11,8 @@ import "zitadel/feature/v2/feature.proto";
 option go_package = "github.com/zitadel/zitadel/pkg/grpc/feature/v2;feature";
 
 message SetInstanceFeaturesRequest{
-  reserved 6;
-  reserved "actions";
+  reserved 3, 6;
+  reserved "oidc_legacy_introspection", "actions";
   optional bool login_default_org = 1 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -25,12 +25,6 @@ message SetInstanceFeaturesRequest{
       description: "Enable projection triggers during an introspection request. This can act as workaround if there are noticeable consistency issues in the introspection response but can have an impact on performance. We are planning to remove triggers for introspection requests in the future. Please raise an issue if you needed to enable this feature.";
     }
   ];
-  optional bool oidc_legacy_introspection = 3 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
 
   optional bool user_schema = 4 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -131,8 +125,8 @@ message GetInstanceFeaturesRequest {
 }
 
 message GetInstanceFeaturesResponse {
-  reserved 7;
-  reserved "actions";
+  reserved 4, 7;
+  reserved "oidc_legacy_introspection", "actions";
   zitadel.object.v2.Details details = 1;
   FeatureFlag login_default_org = 2 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -148,13 +142,6 @@ message GetInstanceFeaturesResponse {
     }
   ];
 
-  FeatureFlag oidc_legacy_introspection = 4 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   FeatureFlag user_schema = 5 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";

proto/zitadel/feature/v2/system.proto

@@ -11,8 +11,8 @@ import "zitadel/feature/v2/feature.proto";
 option go_package = "github.com/zitadel/zitadel/pkg/grpc/feature/v2;feature";
 
 message SetSystemFeaturesRequest{
-  reserved 6;
-  reserved "actions";
+  reserved 3, 6;
+  reserved "oidc_legacy_introspection", "actions";
   optional bool login_default_org = 1 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -27,13 +27,6 @@ message SetSystemFeaturesRequest{
     }
   ];
 
-  optional bool oidc_legacy_introspection = 3 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   optional bool user_schema = 4 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -105,8 +98,8 @@ message ResetSystemFeaturesResponse {
 message GetSystemFeaturesRequest {}
 
 message GetSystemFeaturesResponse {
-  reserved 7;
-  reserved "actions";
+  reserved 4, 7;
+  reserved "oidc_legacy_introspection", "actions";
   zitadel.object.v2.Details details = 1;
   FeatureFlag login_default_org = 2 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -122,13 +115,6 @@ message GetSystemFeaturesResponse {
     }
   ];
 
-  FeatureFlag oidc_legacy_introspection = 4 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   FeatureFlag user_schema = 5 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";

proto/zitadel/feature/v2beta/instance.proto

@@ -11,8 +11,8 @@ import "zitadel/feature/v2beta/feature.proto";
 option go_package = "github.com/zitadel/zitadel/pkg/grpc/feature/v2beta;feature";
 
 message SetInstanceFeaturesRequest{
-  reserved 6;
-  reserved "actions";
+  reserved 3, 6;
+  reserved "oidc_legacy_introspection", "actions";
   optional bool login_default_org = 1 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -25,12 +25,6 @@ message SetInstanceFeaturesRequest{
       description: "Enable projection triggers during an introspection request. This can act as workaround if there are noticeable consistency issues in the introspection response but can have an impact on performance. We are planning to remove triggers for introspection requests in the future. Please raise an issue if you needed to enable this feature.";
     }
   ];
-  optional bool oidc_legacy_introspection = 3 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
 
   optional bool user_schema = 4 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -97,8 +91,8 @@ message GetInstanceFeaturesRequest {
 }
 
 message GetInstanceFeaturesResponse {
-  reserved 7;
-  reserved "actions";
+  reserved 4, 7;
+  reserved "oidc_legacy_introspection", "actions";
   zitadel.object.v2beta.Details details = 1;
   FeatureFlag login_default_org = 2 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -114,13 +108,6 @@ message GetInstanceFeaturesResponse {
     }
   ];
 
-  FeatureFlag oidc_legacy_introspection = 4 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   FeatureFlag user_schema = 5 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";

proto/zitadel/feature/v2beta/system.proto

@@ -11,8 +11,8 @@ import "zitadel/feature/v2beta/feature.proto";
 option go_package = "github.com/zitadel/zitadel/pkg/grpc/feature/v2beta;feature";
 
 message SetSystemFeaturesRequest{
-  reserved 6;
-  reserved "actions";
+  reserved 3, 6;
+  reserved "oidc_legacy_introspection", "actions";
   optional bool login_default_org = 1 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -27,13 +27,6 @@ message SetSystemFeaturesRequest{
     }
   ];
 
-  optional bool oidc_legacy_introspection = 3 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   optional bool user_schema = 4 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";
@@ -78,8 +71,8 @@ message ResetSystemFeaturesResponse {
 message GetSystemFeaturesRequest {}
 
 message GetSystemFeaturesResponse {
-  reserved 7;
-  reserved "actions";
+  reserved 4, 7;
+  reserved "oidc_legacy_introspection", "actions";
   zitadel.object.v2beta.Details details = 1;
   FeatureFlag login_default_org = 2 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
@@ -95,13 +88,6 @@ message GetSystemFeaturesResponse {
     }
   ];
 
-  FeatureFlag oidc_legacy_introspection = 4 [
-    (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
-      example: "true";
-      description: "We have recently refactored the introspection endpoint for performance reasons. This feature can be used to rollback to the legacy implementation if unexpected bugs arise. Please raise an issue if you needed to enable this feature.";
-    }
-  ];
-
   FeatureFlag user_schema = 5 [
     (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_field) = {
       example: "true";