feat: add trusted groups functionality for duty information

- Introduced a new `trusted_groups` table to store groups authorized to receive duty information.
- Implemented functions to add, remove, and check trusted groups in the database.
- Enhanced command handlers to manage trusted groups, including `/trust_group` and `/untrust_group` commands for admin users.
- Updated internationalization messages to support new commands and group status notifications.
- Added unit tests for trusted groups repository functions to ensure correct behavior and data integrity.

duty_teller/db/repository.py

@@ -11,6 +11,7 @@ from duty_teller.db.models import (
     User,
     Duty,
     GroupDutyPin,
+    TrustedGroup,
     CalendarSubscriptionToken,
     Role,
 )
@@ -593,6 +594,71 @@ def get_all_group_duty_pin_chat_ids(session: Session) -> list[int]:
     return [r[0] for r in rows]
 
 
+def is_trusted_group(session: Session, chat_id: int) -> bool:
+    """Check if the chat is in the trusted groups list.
+
+    Args:
+        session: DB session.
+        chat_id: Telegram chat id.
+
+    Returns:
+        True if the group is trusted.
+    """
+    return (
+        session.query(TrustedGroup).filter(TrustedGroup.chat_id == chat_id).first()
+        is not None
+    )
+
+
+def add_trusted_group(
+    session: Session, chat_id: int, added_by_user_id: int | None = None
+) -> TrustedGroup:
+    """Add a group to the trusted list.
+
+    Args:
+        session: DB session.
+        chat_id: Telegram chat id.
+        added_by_user_id: Telegram user id of the admin who added the group (optional).
+
+    Returns:
+        Created TrustedGroup instance.
+    """
+    now_iso = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+    record = TrustedGroup(
+        chat_id=chat_id,
+        added_by_user_id=added_by_user_id,
+        added_at=now_iso,
+    )
+    session.add(record)
+    session.commit()
+    session.refresh(record)
+    return record
+
+
+def remove_trusted_group(session: Session, chat_id: int) -> None:
+    """Remove a group from the trusted list.
+
+    Args:
+        session: DB session.
+        chat_id: Telegram chat id.
+    """
+    session.query(TrustedGroup).filter(TrustedGroup.chat_id == chat_id).delete()
+    session.commit()
+
+
+def get_all_trusted_group_ids(session: Session) -> list[int]:
+    """Return all chat_ids that are trusted.
+
+    Args:
+        session: DB session.
+
+    Returns:
+        List of trusted chat ids.
+    """
+    rows = session.query(TrustedGroup.chat_id).all()
+    return [r[0] for r in rows]
+
+
 def set_user_phone(
     session: Session, telegram_user_id: int, phone: str | None
 ) -> User | None: