feat: add team calendar ICS endpoint and related functionality

- Implemented a new API endpoint to generate an ICS calendar for team duty shifts, accessible via a valid token.
- Enhanced the `calendar_link` command to return both personal and team calendar URLs.
- Added a new function to build the team ICS file, ensuring each event includes the duty holder's name in the description.
- Updated tests to cover the new team calendar functionality, including validation for token formats and response content.
- Revised internationalization messages to reflect the new team calendar links.

tests/test_personal_calendar_ics.py

@@ -4,7 +4,7 @@ from types import SimpleNamespace
 
 from icalendar import Calendar as ICalendar
 
-from duty_teller.api.personal_calendar_ics import build_personal_ics
+from duty_teller.api.personal_calendar_ics import build_personal_ics, build_team_ics
 
 
 # Minimal Duty-like object for build_personal_ics(duties_with_name: list[tuple[Duty, str]])
@@ -45,6 +45,22 @@ def test_build_personal_ics_one_duty():
     assert b"duty-1@duty-teller" in ics or "duty-1@duty-teller" in ics.decode("utf-8")
 
 
+def test_build_team_ics_vevent_has_description_with_full_name():
+    """Team ICS VEVENT includes DESCRIPTION with the duty holder's full_name."""
+    duties = [
+        _duty(1, "2025-02-20T09:00:00Z", "2025-02-20T18:00:00Z", "duty"),
+    ]
+    ics = build_team_ics(duties)
+    cal = ICalendar.from_ical(ics)
+    assert cal is not None
+    events = [c for c in cal.walk() if c.name == "VEVENT"]
+    assert len(events) == 1
+    ev = events[0]
+    assert ev.get("summary") == "Duty"
+    assert ev.get("description") == "Test User"
+    assert b"Team Calendar" in ics or "Team Calendar" in ics.decode("utf-8")
+
+
 def test_build_personal_ics_event_types():
     """Unavailable and vacation get correct SUMMARY."""
     duties = [