Long challenge names don't create forums properly

[jmgasper]

It seems like there is a disconnect between the length of challenge names allowed by WM / Challenge API and what sort of name we can give a forum, with forums not being created for very long challenge names.

We should investigate the limit on Vanilla and apply that to the name field of challenges to ensure that challenges can't be created with names that are too long for Vanilla.

Another possibility is just to truncate the forum name used for challenges if the challenge name is too long