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.

duty_teller/handlers/commands.py

@@ -122,21 +122,30 @@ async def calendar_link(update: Update, context: ContextTypes.DEFAULT_TYPE) -> N
             if not can_access_miniapp_for_telegram_user(session, telegram_user_id):
                 return (None, "denied")
             token = create_calendar_token(session, user.id)
-            base = (config.MINI_APP_BASE_URL or "").rstrip("/")
-            url = f"{base}/api/calendar/ical/{token}.ics" if base else None
-            return (url, None)
+            return (token, None)
 
-    result_url, error = await asyncio.get_running_loop().run_in_executor(
+    result_token, error = await asyncio.get_running_loop().run_in_executor(
         None, do_calendar_link
     )
     if error == "denied":
         await update.message.reply_text(t(lang, "calendar_link.access_denied"))
         return
-    if not result_url:
+    if not result_token:
         await update.message.reply_text(t(lang, "calendar_link.error"))
         return
+    base = (config.MINI_APP_BASE_URL or "").rstrip("/")
+    if not base:
+        await update.message.reply_text(t(lang, "calendar_link.error"))
+        return
+    url_personal = f"{base}/api/calendar/ical/{result_token}.ics"
+    url_team = f"{base}/api/calendar/ical/team/{result_token}.ics"
     await update.message.reply_text(
-        t(lang, "calendar_link.success", url=result_url)
+        t(
+            lang,
+            "calendar_link.success",
+            url_personal=url_personal,
+            url_team=url_team,
+        )
         + "\n\n"
         + t(lang, "calendar_link.help_hint")
     )