Frond End Assistance And Iterative Clean Up

This relates to XX-4076 and XX-4092. This is largely cleaning up documentation for front end. There was also clean up where I identified a bug in the client registration code-path as well a poorly named method off of reception identity.

This also included exposing IsRegisteredWithUd after front end specifically asked for a method to have UD registration context; they need to know if they have to show the page where the user inputs a username if not registered.

bindings/identity.go

@@ -79,7 +79,8 @@ func (c *Cmix) MakeReceptionIdentity() ([]byte, error) {
 }
 
 // MakeLegacyReceptionIdentity generates the legacy identity for receiving
-// messages.
+// messages. As with all legacy calls, this should primarily be used
+// for the xx messenger team.
 func (c *Cmix) MakeLegacyReceptionIdentity() ([]byte, error) {
 	ident, err := xxdk.MakeLegacyReceptionIdentity(c.api)
 	if err != nil {