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/feature/feature.go

@@ -0,0 +1,30 @@
+package feature
+
+//go:generate enumer -type Key -transform snake -trimprefix Key
+type Key int
+
+const (
+	KeyUnspecified Key = iota
+	KeyLoginDefaultOrg
+	KeyTriggerIntrospectionProjections
+	KeyLegacyIntrospection
+)
+
+//go:generate enumer -type Level -transform snake -trimprefix Level
+type Level int
+
+const (
+	LevelUnspecified Level = iota
+	LevelSystem
+	LevelInstance
+	LevelOrg
+	LevelProject
+	LevelApp
+	LevelUser
+)
+
+type Features struct {
+	LoginDefaultOrg                 bool `json:"login_default_org,omitempty"`
+	TriggerIntrospectionProjections bool `json:"trigger_introspection_projections,omitempty"`
+	LegacyIntrospection             bool `json:"legacy_introspection,omitempty"`
+}