Add /_dendrite/admin/evacuateRoom/{roomID} (#2401)

* Add new endpoint to allow admins to evacuate the local server from the room

* Guard endpoint

* Use right prefix

* Auth API

* More useful return error rather than a panic

* More useful return value again

* Update the path

* Try using inputer instead

* oh provide the config

* Try that again

* Return affected user IDs

* Don't create so many forward extremities

* Add missing `Path` to name

Co-authored-by: Till <2353100+S7evinK@users.noreply.github.com>

roomserver/internal/api.go

@@ -35,6 +35,7 @@ type RoomserverInternalAPI struct {
 	*perform.Backfiller
 	*perform.Forgetter
 	*perform.Upgrader
+	*perform.Admin
 	ProcessContext         *process.ProcessContext
 	DB                     storage.Database
 	Cfg                    *config.RoomServer
@@ -164,6 +165,12 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.FederationInternalA
 		Cfg:    r.Cfg,
 		URSAPI: r,
 	}
+	r.Admin = &perform.Admin{
+		DB:      r.DB,
+		Cfg:     r.Cfg,
+		Inputer: r.Inputer,
+		Queryer: r.Queryer,
+	}
 
 	if err := r.Inputer.Start(); err != nil {
 		logrus.WithError(err).Panic("failed to start roomserver input API")