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/authcode.py

@@ -0,0 +1,113 @@
+"""
+Authorization code management for OIDC and cookie exchange flows.
+
+Codes are short-lived (60 seconds) and stored in-memory only.
+Two separate stores maintain full isolation between OIDC and cookie flows.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+import secrets
+from datetime import UTC, datetime, timedelta
+
+import msgspec
+
+_logger = logging.getLogger(__name__)
+
+# Auth codes expire after this duration
+AUTH_CODE_LIFETIME = timedelta(seconds=60)
+
+
+class OIDCCode(msgspec.Struct):
+    """An OIDC authorization code pending token exchange.
+
+    PKCE uses S256 only when provided (verified at token exchange).
+    """
+
+    session_key: str
+    created: datetime
+    redirect_uri: str
+    scope: str
+    nonce: str | None = None
+    code_challenge: str | None = None
+
+
+class CookieCode(msgspec.Struct):
+    """A cookie exchange code for setting session cookie after WebSocket auth."""
+
+    session_key: str
+    created: datetime
+
+
+# Separate stores for each code type
+oidc_codes: dict[str, OIDCCode] = {}
+cookie_codes: dict[str, CookieCode] = {}
+
+# Background cleanup task
+_cleanup_task: asyncio.Task | None = None
+
+
+async def start():
+    """Start the cleanup background task."""
+    global _cleanup_task
+    if _cleanup_task is None:
+        _cleanup_task = asyncio.create_task(_cleanup_loop())
+
+
+async def stop():
+    """Stop the cleanup background task."""
+    global _cleanup_task
+    if _cleanup_task:
+        _cleanup_task.cancel()
+        try:
+            await _cleanup_task
+        except asyncio.CancelledError:
+            pass
+        _cleanup_task = None
+
+
+async def _cleanup_loop():
+    while True:
+        try:
+            await asyncio.sleep(30)  # Check every 30 seconds
+            _cleanup_expired()
+        except asyncio.CancelledError:
+            break
+        except Exception:
+            _logger.exception("Error in auth code cleanup loop")
+
+
+def _cleanup_expired():
+    oldest = datetime.now(UTC) - AUTH_CODE_LIFETIME
+    for code, auth_code in list(oidc_codes.items()):
+        if auth_code.created < oldest:
+            del oidc_codes[code]
+    for code, auth_code in list(cookie_codes.items()):
+        if auth_code.created < oldest:
+            del cookie_codes[code]
+
+
+def store_oidc(code: OIDCCode) -> str:
+    """Store an OIDC authorization code and return the code string."""
+    token = secrets.token_urlsafe(12)
+    oidc_codes[token] = code
+    return token
+
+
+def consume_oidc(token: str) -> OIDCCode | None:
+    """Consume an OIDC code, returning it if valid. Atomic removal."""
+    return oidc_codes.pop(token, None)
+
+
+def store_cookie(code: CookieCode) -> str:
+    """Store a cookie exchange code and return the code string."""
+    token = secrets.token_urlsafe(12)
+    cookie_codes[token] = code
+    return token
+
+
+def consume_cookie(token: str) -> CookieCode | None:
+    """Consume a cookie exchange code, returning it if valid. Atomic removal."""
+    return cookie_codes.pop(token, None)