OAuth callback endpoint for provider-specific flows (most providers use GET).
Response varies based on the original OAuth initiation:
insforge_code for exchange endpointaccess_token and sets httpOnly cookiegoogle, github, discord, linkedin, facebook, instagram, tiktok, apple, x, spotify, microsoft Authorization code from OAuth provider
JWT state with redirect URI and optional code_challenge
Direct ID token (for some providers)
Redirect to application.