OAuth2 OpenID Connect provider support, API and DB refactoring (#3)

Allows Paskia to authenticate the user to a client site.
- User friendly client registration flow on the admin app
- Redirect-based authentication flow (per spec)
- Backchannel logout both ways to keep sessions synchronized
- Groups integrated with Paskia's permission system
- Adds email, preferred username and telephone fields on user profile
- All new user basic info layout to show the new information, better looks
- API and DB structures redesigned
- Various unrelated fixes to theming and layout

paskia-js/src/overlay.ts

@@ -57,6 +57,7 @@ export class AuthCancelledError extends Error {
 }
 
 export function holdGlobalBackdrop(): void {
+  injectStyles()
   backdropHolders++
   document.body.classList.add('paskia-backdrop')
 }