The Growth-Team is working on a structured mentor list as part of T264343. One of the goals for this project is to make it easy to validate the mentor list content when a mentor signs up or changes their details (such as, message). It turns out we don't validate the maximum message length in Special:EnrollAsMentor (at least, I didn't check the message change dialog yet).
https://en.wikipedia.beta.wmflabs.org/w/index.php?title=MediaWiki:GrowthMentors.json&diff=552390&oldid=552389 is an example of a change that should not be possible.
Ticket origin: @KStoller-WMF's comment at T312102#8058414.
Acceptance criteria
- When structured mentor list is enabled, Special:EnrollAsMentor does not let soon-to-be mentors to enter an introduction message that's longer than the prescribed limit (as of today, 240 characters)
- When structured mentor list is enabled, mentors are not able to set a longer introduction message than 240 characters via Special:MentorDashboard.