Have repo JIRA link support comma-separated list of multiple project keys (BB-10331)

On the Settings (gear) -> Links page of a repository:

It would be very helpful to allow a list (comma or pipe separated, perhaps) of JIRA project keys when creating/editing a Link to JIRA.

Currently, you either have to create a whole series of JIRA Links (all with the same URL), or use a Custom Link with a crazy regex like this:

#!python

((?<!\w)((MPH|CENT|TTXT|TTCW|TTEA|TSMA)-\d+)(?!\w))