Add internationalization support and enhance language handling

- Introduced a new i18n module for managing translations and language normalization, supporting both Russian and English.
- Updated various handlers and services to utilize the new translation functions for user-facing messages, improving user experience based on language preferences.
- Enhanced error handling and response messages to be language-aware, ensuring appropriate feedback is provided to users in their preferred language.
- Added tests for the i18n module to validate language detection and translation functionality.
- Updated the example environment file to include a default language configuration.

duty_teller/handlers/group_duty_pin.py

@@ -11,6 +11,7 @@ from telegram.error import BadRequest, Forbidden
 from telegram.ext import ChatMemberHandler, CommandHandler, ContextTypes
 
 from duty_teller.db.session import session_scope
+from duty_teller.i18n import get_lang, t
 from duty_teller.services.group_duty_pin_service import (
     get_duty_message_text,
     get_next_shift_end_utc,
@@ -26,9 +27,9 @@ JOB_NAME_PREFIX = "duty_pin_"
 RETRY_WHEN_NO_DUTY_MINUTES = 15
 
 
-def _get_duty_message_text_sync() -> str:
+def _get_duty_message_text_sync(lang: str = "en") -> str:
     with session_scope(config.DATABASE_URL) as session:
-        return get_duty_message_text(session, config.DUTY_DISPLAY_TZ)
+        return get_duty_message_text(session, config.DUTY_DISPLAY_TZ, lang)
 
 
 def _get_next_shift_end_sync():
@@ -98,7 +99,9 @@ async def update_group_pin(context: ContextTypes.DEFAULT_TYPE) -> None:
     if message_id is None:
         logger.info("No pin record for chat_id=%s, skipping update", chat_id)
         return
-    text = await loop.run_in_executor(None, _get_duty_message_text_sync)
+    text = await loop.run_in_executor(
+        None, lambda: _get_duty_message_text_sync(config.DEFAULT_LANGUAGE)
+    )
     try:
         await context.bot.edit_message_text(
             chat_id=chat_id,
@@ -133,7 +136,10 @@ async def my_chat_member_handler(
         ChatMemberStatus.BANNED,
     ):
         loop = asyncio.get_running_loop()
-        text = await loop.run_in_executor(None, _get_duty_message_text_sync)
+        lang = get_lang(update.effective_user)
+        text = await loop.run_in_executor(
+            None, lambda: _get_duty_message_text_sync(lang)
+        )
         try:
             msg = await context.bot.send_message(chat_id=chat_id, text=text)
         except (BadRequest, Forbidden) as e:
@@ -154,9 +160,7 @@ async def my_chat_member_handler(
             try:
                 await context.bot.send_message(
                     chat_id=chat_id,
-                    text="Сообщение о дежурстве отправлено, но закрепить его не удалось. "
-                    "Сделайте бота администратором с правом «Закреплять сообщения» (Pin messages), "
-                    "затем отправьте в чат команду /pin_duty — текущее сообщение будет закреплено.",
+                    text=t(lang, "pin_duty.could_not_pin_make_admin"),
                 )
             except (BadRequest, Forbidden):
                 pass
@@ -190,19 +194,18 @@ async def restore_group_pin_jobs(application) -> None:
 
 
 async def pin_duty_cmd(update: Update, context: ContextTypes.DEFAULT_TYPE) -> None:
-    if not update.message or not update.effective_chat:
+    if not update.message or not update.effective_chat or not update.effective_user:
         return
     chat = update.effective_chat
+    lang = get_lang(update.effective_user)
     if chat.type not in ("group", "supergroup"):
-        await update.message.reply_text("Команда /pin_duty работает только в группах.")
+        await update.message.reply_text(t(lang, "pin_duty.group_only"))
         return
     chat_id = chat.id
     loop = asyncio.get_running_loop()
     message_id = await loop.run_in_executor(None, _sync_get_message_id, chat_id)
     if message_id is None:
-        await update.message.reply_text(
-            "В этом чате ещё нет сообщения о дежурстве. Добавьте бота в группу — оно создастся автоматически."
-        )
+        await update.message.reply_text(t(lang, "pin_duty.no_message"))
         return
     try:
         await context.bot.pin_chat_message(
@@ -210,12 +213,10 @@ async def pin_duty_cmd(update: Update, context: ContextTypes.DEFAULT_TYPE) -> No
             message_id=message_id,
             disable_notification=True,
         )
-        await update.message.reply_text("Сообщение о дежурстве закреплено.")
+        await update.message.reply_text(t(lang, "pin_duty.pinned"))
     except (BadRequest, Forbidden) as e:
         logger.warning("pin_duty failed chat_id=%s: %s", chat_id, e)
-        await update.message.reply_text(
-            "Не удалось закрепить. Убедитесь, что бот — администратор с правом «Закреплять сообщения»."
-        )
+        await update.message.reply_text(t(lang, "pin_duty.failed"))
 
 
 group_duty_pin_handler = ChatMemberHandler(