Licensing service (#19903)

* Licensing: supplies a service to handle licensing information

* Licensing: uses the license service further

Uses the license service instead of settings.isEnterprise:
- external team members
- saml
- usage stats

* Licensing: fixes broken tests due to new Licensing service dependency

* Licensing: fixes linting errors

* Licensing: exposes license expiry information to the frontend

pkg/api/http_server.go

@@ -69,6 +69,7 @@ type HTTPServer struct {
 	RemoteCacheService  *remotecache.RemoteCache `inject:""`
 	ProvisioningService ProvisioningService      `inject:""`
 	Login               *login.LoginService      `inject:""`
+	License             models.Licensing         `inject:""`
 }
 
 func (hs *HTTPServer) Init() error {