reload configuration also in case a custom workspaces gets assigned to the config topic

[mukil]

Currently the configuration option "custom workspace membership" only gets in effect if the "Sign-up Configuration" topic is next updated ("Edit" and "Ok does the trick) . But this is, of course a usability bug and inconvenient for users.

Therefore we could probably improve this through implementing a listener to postCreateAssociation()..

[mukil]

I won't fix this because i do not want the sign-up plugin to listen on every association created in the system (just to check if it affects sign-up plugin configuration) and i currently do not know of any other clever way. Possibly the best (cleanest) option is to include this "custom workspace" relation in the "Sign-up Configuration" topic type definition.