This resolves ENG-8263, but most of the work was done in the parent.

Depends on D12241

Tested invite link flow end-to-end on web by creating an invite link as a keyserver admin, and then opening it in an Incognito tab as another user, and confirming I am able to join

Opted not to test native at all, but can test that too if helpful, and especially if we suspect this RegExp is further duplicated elsewhere.