We should allow users to integrate their GitHub account into their current account.

Some quick thoughts around this:

• We need to be able to associate most records (like Comment and Task) to a User that created them
• A User could be created by signing up with email, but could also be created via webhooks by some action on GitHub (or some other service)
• We can’t assume a user has an email associated with their account (GitHub may not provide this)
• Emails should be broken off as separate identity providers
• A GitHub account is also an identity provider
• When a user was created due to an external identity provider (claimed vs unclaimed), that user can be merged
• Merging will copy all relevant data from that user to the new user
• We probably need to punt on a user signing up / signing in with GitHub – they can only connect an account later – otherwise we could have a scenario where someone intends to connect a Code Corps account to a GitHub account, but instead creates two separate accounts (one via email, one via GitHub) that are now disconnected. This would mean we'd have to some complex two-step verification process for a merge, which is beyond the scope of MVP here.