- move OAuth-related fields off of api_keys into a new user_links table
- restrict users to single form of login
- process updates to user email/usernames for OIDC
- added a login_type column to users
This enables a "kubernetes_pod" to attach multiple agents that
could be for multiple services. Each agent is required to have
a unique name, so SSH syntax is:
`coder ssh <workspace>.<agent>`
A resource can have zero agents too, they aren't required.
