models: boards: add PUT members entry point
models: boards: add PUT members entry point

Allows to change the members from the API.

wekan/wekan,libreboard/libreboard,wekan/wekan,GhassenRjab/wekan,GhassenRjab/wekan,wekan/wekan,wekan/wekan,libreboard/libreboard,GhassenRjab/wekan,wekan/wekan