source-gitlab: Unique Behaviors

1. Single-Use Rotating Refresh Tokens

GitLab's OAuth implementation issues single-use refresh tokens. Every time an access token is refreshed, the old refresh token is invalidated and a new one is returned. The connector uses refresh_token_updater to persist the new refresh token back to the connection configuration after each token exchange.

Why this matters: If a token refresh succeeds but the new refresh token fails to persist (e.g., due to a crash or network issue between the exchange and the config update), the connection becomes permanently broken and requires re-authentication. Standard OAuth connectors can retry with the same refresh token, but GitLab cannot.