feat: exchange gRPC server implementation to connectRPC (#10145)

# Which Problems Are Solved

The current maintained gRPC server in combination with a REST (grpc)
gateway is getting harder and harder to maintain. Additionally, there
have been and still are issues with supporting / displaying `oneOf`s
correctly.
We therefore decided to exchange the server implementation to
connectRPC, which apart from supporting connect as protocol, also also
"standard" gRCP clients as well as HTTP/1.1 / rest like clients, e.g.
curl directly call the server without any additional gateway.

# How the Problems Are Solved

- All v2 services are moved to connectRPC implementation. (v1 services
are still served as pure grpc servers)
- All gRPC server interceptors were migrated / copied to a corresponding
connectRPC interceptor.
- API.ListGrpcServices and API. ListGrpcMethods were changed to include
the connect services and endpoints.
- gRPC server reflection was changed to a `StaticReflector` using the
`ListGrpcServices` list.
- The `grpc.Server` interfaces was split into different combinations to
be able to handle the different cases (grpc server and prefixed gateway,
connect server with grpc gateway, connect server only, ...)
- Docs of services serving connectRPC only with no additional gateway
(instance, webkey, project, app, org v2 beta) are changed to expose that
- since the plugin is not yet available on buf, we download it using
`postinstall` hook of the docs

# Additional Changes

- WebKey service is added as v2 service (in addition to the current
v2beta)

# Additional Context

closes #9483

---------

Co-authored-by: Elio Bischof <elio@zitadel.com>

internal/api/grpc/action/v2beta/query.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"strings"
 
+	"connectrpc.com/connect"
 	"google.golang.org/protobuf/types/known/durationpb"
 	"google.golang.org/protobuf/types/known/timestamppb"
 
@@ -22,14 +23,14 @@ const (
 	conditionIDEventGroupSegmentCount             = 1
 )
 
-func (s *Server) GetTarget(ctx context.Context, req *action.GetTargetRequest) (*action.GetTargetResponse, error) {
-	resp, err := s.query.GetTargetByID(ctx, req.GetId())
+func (s *Server) GetTarget(ctx context.Context, req *connect.Request[action.GetTargetRequest]) (*connect.Response[action.GetTargetResponse], error) {
+	resp, err := s.query.GetTargetByID(ctx, req.Msg.GetId())
 	if err != nil {
 		return nil, err
 	}
-	return &action.GetTargetResponse{
+	return connect.NewResponse(&action.GetTargetResponse{
 		Target: targetToPb(resp),
-	}, nil
+	}), nil
 }
 
 type InstanceContext interface {
@@ -41,8 +42,8 @@ type Context interface {
 	GetOwner() InstanceContext
 }
 
-func (s *Server) ListTargets(ctx context.Context, req *action.ListTargetsRequest) (*action.ListTargetsResponse, error) {
-	queries, err := s.ListTargetsRequestToModel(req)
+func (s *Server) ListTargets(ctx context.Context, req *connect.Request[action.ListTargetsRequest]) (*connect.Response[action.ListTargetsResponse], error) {
+	queries, err := s.ListTargetsRequestToModel(req.Msg)
 	if err != nil {
 		return nil, err
 	}
@@ -50,14 +51,14 @@ func (s *Server) ListTargets(ctx context.Context, req *action.ListTargetsRequest
 	if err != nil {
 		return nil, err
 	}
-	return &action.ListTargetsResponse{
+	return connect.NewResponse(&action.ListTargetsResponse{
 		Result:     targetsToPb(resp.Targets),
 		Pagination: filter.QueryToPaginationPb(queries.SearchRequest, resp.SearchResponse),
-	}, nil
+	}), nil
 }
 
-func (s *Server) ListExecutions(ctx context.Context, req *action.ListExecutionsRequest) (*action.ListExecutionsResponse, error) {
-	queries, err := s.ListExecutionsRequestToModel(req)
+func (s *Server) ListExecutions(ctx context.Context, req *connect.Request[action.ListExecutionsRequest]) (*connect.Response[action.ListExecutionsResponse], error) {
+	queries, err := s.ListExecutionsRequestToModel(req.Msg)
 	if err != nil {
 		return nil, err
 	}
@@ -65,10 +66,10 @@ func (s *Server) ListExecutions(ctx context.Context, req *action.ListExecutionsR
 	if err != nil {
 		return nil, err
 	}
-	return &action.ListExecutionsResponse{
+	return connect.NewResponse(&action.ListExecutionsResponse{
 		Result:     executionsToPb(resp.Executions),
 		Pagination: filter.QueryToPaginationPb(queries.SearchRequest, resp.SearchResponse),
-	}, nil
+	}), nil
 }
 
 func targetsToPb(targets []*query.Target) []*action.Target {