Create new accounts from course's home wiki when possible

[ragesoss]

Current Behavior:

Both accounts created through the Dashboard itself (via account requests) and also new accounts that get created by users starting from an enroll link go to English Wikipedia. For events on other wikis, this can be confusing and also does not correctly attributed that user's own language as their home wiki since their account gets created on en.wiki.

Desired Behavior:

When possible, accounts should be created through a user's home wiki. This will need to be extensively tested for compatibility with immediate OAuth login, and also needs to account for the situation where the account creation limit has been reached and the Dashboard would need to fall back on a bot account (https://en.wikipedia.org/wiki/User:OutreachDashboardBot) that is only able to create en.wiki accounts beyond the limit.

[Abishekcs]

Working on this 😄.

[ragesoss]

The issue description is somewhat incomplete, as the system does already use other wikis to create accounts in some cases (ie, account requests), but only in limited circumstances. It may be best to think of this as two issues, one for requested accounts and the other for enrollment links.

The OAuth integration is the key part for enrollment links.