perf(oidc): disable push of user token meta-event (#8691)

# Which Problems Are Solved

When executing many concurrent authentication requests on a single
machine user, there were performance issues. As the same aggregate is
being searched and written to concurrently, we traced it down to a
locking issue on the used index.
We already optimized the token endpoint by creating a separate OIDC
aggregate.

At the time we decided to push a single event to the user aggregate, for
the user audit log. See [technical advisory
10010](https://zitadel.com/docs/support/advisory/a10010) for more
details.

However, a recent security fix introduced an additional search query on
the user aggregate, causing the locking issue we found.

# How the Problems Are Solved

Add a feature flag which disables pushing of the `user.token.v2.added`.
The event has no importance and was only added for informational
purposes on the user objects. The `oidc_session.access_token.added` is
the actual payload event and is pushed on the OIDC session aggregate and
can still be used for audit trail.

# Additional Changes

- Fix an event mapper type for
`SystemOIDCSingleV1SessionTerminationEventType`

# Additional Context

- Reported by support request
- https://github.com/zitadel/zitadel/pull/7822 changed the token
aggregate
- https://github.com/zitadel/zitadel/pull/8631 introduced user state
check

Load test trace graph with `user.token.v2.added` **enabled**. Query
times are steadily increasing:


![image](https://github.com/user-attachments/assets/4aa25055-8721-4e93-b695-625560979909)

Load test trace graph with `user.token.v2.added` **disabled**. Query
times constant:


![image](https://github.com/user-attachments/assets/a7657f6c-0c55-401b-8291-453da5d5caf9)

---------

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

internal/query/instance_features.go

@@ -19,6 +19,7 @@ type InstanceFeatures struct {
 	WebKey                          FeatureSource[bool]
 	DebugOIDCParentError            FeatureSource[bool]
 	OIDCSingleV1SessionTermination  FeatureSource[bool]
+	DisableUserTokenEvent           FeatureSource[bool]
 }
 
 func (q *Queries) GetInstanceFeatures(ctx context.Context, cascade bool) (_ *InstanceFeatures, err error) {

internal/query/instance_features_model.go

@@ -70,6 +70,7 @@ func (m *InstanceFeaturesReadModel) Query() *eventstore.SearchQueryBuilder {
 			feature_v2.InstanceWebKeyEventType,
 			feature_v2.InstanceDebugOIDCParentErrorEventType,
 			feature_v2.InstanceOIDCSingleV1SessionTerminationEventType,
+			feature_v2.InstanceDisableUserTokenEvent,
 		).
 		Builder().ResourceOwner(m.ResourceOwner)
 }
@@ -94,6 +95,7 @@ func (m *InstanceFeaturesReadModel) populateFromSystem() bool {
 	m.instance.Actions = m.system.Actions
 	m.instance.ImprovedPerformance = m.system.ImprovedPerformance
 	m.instance.OIDCSingleV1SessionTermination = m.system.OIDCSingleV1SessionTermination
+	m.instance.DisableUserTokenEvent = m.system.DisableUserTokenEvent
 	return true
 }
 
@@ -125,6 +127,8 @@ func reduceInstanceFeatureSet[T any](features *InstanceFeatures, event *feature_
 		features.DebugOIDCParentError.set(level, event.Value)
 	case feature.KeyOIDCSingleV1SessionTermination:
 		features.OIDCSingleV1SessionTermination.set(level, event.Value)
+	case feature.KeyDisableUserTokenEvent:
+		features.DisableUserTokenEvent.set(level, event.Value)
 	}
 	return nil
 }

internal/query/projection/instance_features.go

@@ -100,6 +100,10 @@ func (*instanceFeatureProjection) Reducers() []handler.AggregateReducer {
 				Event:  feature_v2.InstanceOIDCSingleV1SessionTerminationEventType,
 				Reduce: reduceInstanceSetFeature[bool],
 			},
+			{
+				Event:  feature_v2.InstanceDisableUserTokenEvent,
+				Reduce: reduceInstanceSetFeature[bool],
+			},
 			{
 				Event:  instance.InstanceRemovedEventType,
 				Reduce: reduceInstanceRemovedHelper(InstanceDomainInstanceIDCol),

internal/query/projection/system_features.go

@@ -80,6 +80,10 @@ func (*systemFeatureProjection) Reducers() []handler.AggregateReducer {
 				Event:  feature_v2.SystemImprovedPerformanceEventType,
 				Reduce: reduceSystemSetFeature[[]feature.ImprovedPerformanceType],
 			},
+			{
+				Event:  feature_v2.SystemDisableUserTokenEvent,
+				Reduce: reduceSystemSetFeature[bool],
+			},
 		},
 	}}
 }

internal/query/system_features.go

@@ -28,6 +28,7 @@ type SystemFeatures struct {
 	Actions                         FeatureSource[bool]
 	ImprovedPerformance             FeatureSource[[]feature.ImprovedPerformanceType]
 	OIDCSingleV1SessionTermination  FeatureSource[bool]
+	DisableUserTokenEvent           FeatureSource[bool]
 }
 
 func (q *Queries) GetSystemFeatures(ctx context.Context) (_ *SystemFeatures, err error) {

internal/query/system_features_model.go

@@ -58,6 +58,7 @@ func (m *SystemFeaturesReadModel) Query() *eventstore.SearchQueryBuilder {
 			feature_v2.SystemActionsEventType,
 			feature_v2.SystemImprovedPerformanceEventType,
 			feature_v2.SystemOIDCSingleV1SessionTerminationEventType,
+			feature_v2.SystemDisableUserTokenEvent,
 		).
 		Builder().ResourceOwner(m.ResourceOwner)
 }
@@ -91,6 +92,8 @@ func reduceSystemFeatureSet[T any](features *SystemFeatures, event *feature_v2.S
 		features.ImprovedPerformance.set(level, event.Value)
 	case feature.KeyOIDCSingleV1SessionTermination:
 		features.OIDCSingleV1SessionTermination.set(level, event.Value)
+	case feature.KeyDisableUserTokenEvent:
+		features.DisableUserTokenEvent.set(level, event.Value)
 	}
 	return nil
 }