Project page now shows "Ask to join project" button for org members

[rmunn]

Fixes #1153.

Org members who aren't yet project members can ask to join a project by clicking the button, which will send an email to project managers.

Pops up a persistent notification that won't time out:

[github-actions]

UI unit Tests

12 tests  ±0   12 ✅ ±0   0s ⏱️ ±0s
 4 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 28087b2. ± Comparison against base commit 30c8d5a.

[github-actions]

C# Unit Tests

104 tests  ±0   104 ✅ ±0   5s ⏱️ ±0s
 16 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 28087b2. ± Comparison against base commit 30c8d5a.

[rmunn]

One issue that came up when I tested it, but shouldn't arise in production: the elawa project, at the time I tested this, had no members and so there was nobody to send the email to, yet the notification falsely told the user that the project managers had been emailed. However, in production we have a rule that projects without managers aren't allowed, so I think it's safe to ignore that situation.