Fix authentication error handling

[anbraten]

closes #3380

Changes

• [x] Fix issues that errors where not shown on login page (Error component not imported)
• [x] Enhance error messages shown on login page
  • [x] We now show more reasons an error occurred (exp: org not allowed)
  • [x] We now show the error message, description and link the uri in case they were provided by the forge
• [x] Remove duplicated redirecting
  • [x] Login page redirect to /authorize directly instead of /login
  • [x] Rename /do-login route in UI to /login as route isn't part of the backend anymore
• [x] Catch oauth from forges directly in /authorize (was previously passed to forge.Login and returned back again 😅 )
• [x] Pass state as part of OAuthRequest (this will allow us to use a proper state in the next PR)
• [x] rename u to user and tmpUser to userFromForge
• [x] mark /authorize/token as deprecated as its not used

[woodpecker-bot]

Deployment of preview was torn down