feat(api): feature flags (#7356)

* feat(api): feature API proto definitions

* update proto based on discussion with @livio-a

* cleanup old feature flag stuff

* authz instance queries

* align defaults

* projection definitions

* define commands and event reducers

* implement system and instance setter APIs

* api getter implementation

* unit test repository package

* command unit tests

* unit test Get queries

* grpc converter unit tests

* migrate the V1 features

* migrate oidc to dynamic features

* projection unit test

* fix instance by host

* fix instance by id data type in sql

* fix linting errors

* add system projection test

* fix behavior inversion

* resolve proto file comments

* rename SystemDefaultLoginInstanceEventType to SystemLoginDefaultOrgEventType so it's consistent with the instance level event

* use write models and conditional set events

* system features integration tests

* instance features integration tests

* error on empty request

* documentation entry

* typo in feature.proto

* fix start unit tests

* solve linting error on key case switch

* remove system defaults after discussion with @eliobischof

* fix system feature projection

* resolve comments in defaults.yaml

---------

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

internal/query/system_features.go

@@ -0,0 +1,30 @@
+package query
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/domain"
+	"github.com/zitadel/zitadel/internal/feature"
+)
+
+type FeatureSource[T any] struct {
+	Level feature.Level
+	Value T
+}
+
+type SystemFeatures struct {
+	Details *domain.ObjectDetails
+
+	LoginDefaultOrg                 FeatureSource[bool]
+	TriggerIntrospectionProjections FeatureSource[bool]
+	LegacyIntrospection             FeatureSource[bool]
+}
+
+func (q *Queries) GetSystemFeatures(ctx context.Context) (_ *SystemFeatures, err error) {
+	m := NewSystemFeaturesReadModel()
+	if err := q.eventstore.FilterToQueryReducer(ctx, m); err != nil {
+		return nil, err
+	}
+	m.system.Details = readModelToObjectDetails(m.ReadModel)
+	return m.system, nil
+}