Implement phone number normalization and access control for Telegram users

- Added functionality to normalize phone numbers for comparison, ensuring only digits are stored and checked.
- Updated configuration to include optional phone number allowlists for users and admins in the environment settings.
- Enhanced authentication logic to allow access based on normalized phone numbers, in addition to usernames.
- Introduced new helper functions for parsing and validating phone numbers, improving code organization and maintainability.
- Added unit tests to validate phone normalization and access control based on phone numbers.

duty_teller/db/repository.py

@@ -7,6 +7,11 @@ from sqlalchemy.orm import Session
 from duty_teller.db.models import User, Duty, GroupDutyPin
 
 
+def get_user_by_telegram_id(session: Session, telegram_user_id: int) -> User | None:
+    """Find user by telegram_user_id. Returns None if not found (no creation)."""
+    return session.query(User).filter(User.telegram_user_id == telegram_user_id).first()
+
+
 def get_or_create_user(
     session: Session,
     telegram_user_id: int,
@@ -15,7 +20,7 @@ def get_or_create_user(
     first_name: str | None = None,
     last_name: str | None = None,
 ) -> User:
-    user = session.query(User).filter(User.telegram_user_id == telegram_user_id).first()
+    user = get_user_by_telegram_id(session, telegram_user_id)
     if user:
         user.full_name = full_name
         user.username = username