[feature] Process outgoing Move from clientAPI (#2750)

* prevent moved accounts from taking create-type actions

* update move logic

* federate move out

* indicate on web profile when an account has moved

* [docs] Add migration docs section

* lock while checking + setting move state

* use redirectFollowers func for clientAPI as well

* comment typo

* linter? i barely know 'er!

* Update internal/uris/uri.go

Co-authored-by: Daenney <daenney@users.noreply.github.com>

* add a couple tests for move

* fix little mistake exposed by tests (thanks tests)

* ensure Move marked as successful

* attach shared util funcs to struct

* lock whole account when doing move

* move moving check to after error check

* replace repeated text with error func

* linterrrrrr!!!!

* catch self follow case

---------

Co-authored-by: Daenney <daenney@users.noreply.github.com>

internal/api/client/timelines/public.go

@@ -124,6 +124,13 @@ func (m *Module) PublicTimelineGETHandler(c *gin.Context) {
 		return
 	}
 
+	if authed.Account != nil && authed.Account.IsMoving() {
+		// For moving/moved accounts, just return
+		// empty to avoid breaking client apps.
+		apiutil.Data(c, http.StatusOK, apiutil.AppJSON, apiutil.EmptyJSONArray)
+		return
+	}
+
 	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
 		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
 		return