AuthN: New service to support multiple authentication providers for plugins (#75979)

* OnGoing

* Continue migrating structure

* Comment

* Add intermediary service

* Remove unused error so far

* no need for fmt use errors

* use RoleNone

* Docs

* Fix test

* Accounting for review feedback

* Rename oauthserver.ExternalService to OAuthClient

* Revert as the interface looks weird

* Update pluginintegration

* Rename oauthserver.ExternalService

* closer to what it was before

pkg/server/wire.go

@@ -63,8 +63,10 @@ import (
 	datasourceservice "github.com/grafana/grafana/pkg/services/datasources/service"
 	"github.com/grafana/grafana/pkg/services/encryption"
 	encryptionservice "github.com/grafana/grafana/pkg/services/encryption/service"
+	"github.com/grafana/grafana/pkg/services/extsvcauth"
 	"github.com/grafana/grafana/pkg/services/extsvcauth/oauthserver"
 	"github.com/grafana/grafana/pkg/services/extsvcauth/oauthserver/oasimpl"
+	extsvcreg "github.com/grafana/grafana/pkg/services/extsvcauth/registry"
 	"github.com/grafana/grafana/pkg/services/featuremgmt"
 	"github.com/grafana/grafana/pkg/services/folder"
 	"github.com/grafana/grafana/pkg/services/folder/folderimpl"
@@ -358,9 +360,11 @@ var wireBasicSet = wire.NewSet(
 	authnimpl.ProvideAuthnService,
 	supportbundlesimpl.ProvideService,
 	oasimpl.ProvideService,
+	wire.Bind(new(oauthserver.OAuth2Server), new(*oasimpl.OAuth2ServiceImpl)),
+	extsvcreg.ProvideExtSvcRegistry,
+	wire.Bind(new(extsvcauth.ExternalServiceRegistry), new(*extsvcreg.Registry)),
 	anonstore.ProvideAnonDBStore,
 	wire.Bind(new(anonstore.AnonStore), new(*anonstore.AnonDBStore)),
-	wire.Bind(new(oauthserver.OAuth2Server), new(*oasimpl.OAuth2ServiceImpl)),
 	loggermw.Provide,
 	signingkeysimpl.ProvideEmbeddedSigningKeysService,
 	wire.Bind(new(signingkeys.Service), new(*signingkeysimpl.Service)),