Should check IsMember before posting

[jefft0]

If a user is has not been invited as a member of the board, posting a message fails with the error "Unknown". So, before calling CreateThread, etc. we should do a qEval for IsMember . If this returns false then we need to tell the user to get invited by the board administrator.

At some point, boards2/v1 will support an "open board" where the user can post without being invited. We will check for this too.

[jefft0]

Closing as can't implement. See the description of PR #16 .
"Remove dead canCreate support for threads. Previously, it was possible to check if the user is a member of a board to know if they can create a thread. But the new boards2 permission system is more complex and there is no simple test"