[3.x] Bot API 6.0 (#890)

* Base implementation

* Bump license

* Revert re-generated tests

* Fix tests, improved docs

* Remove TODO

* Removed unreachable code

* Changed type of `last_synchronization_error_date`

* Fixed wrongly cleaned code

examples/web_app/handlers.py

@@ -0,0 +1,48 @@
+from aiogram import Bot, F, Router
+from aiogram.dispatcher.filters import Command
+from aiogram.types import (
+    InlineKeyboardButton,
+    InlineKeyboardMarkup,
+    MenuButtonWebApp,
+    Message,
+    WebAppInfo,
+)
+
+my_router = Router()
+
+
+@my_router.message(Command(commands=["start"]))
+async def command_start(message: Message, bot: Bot, base_url: str):
+    await bot.set_chat_menu_button(
+        chat_id=message.chat.id,
+        menu_button=MenuButtonWebApp(text="Open Menu", web_app=WebAppInfo(url=f"{base_url}/demo")),
+    )
+    await message.answer("""Hi!\nSend me any type of message to start.\nOr just send /webview""")
+
+
+@my_router.message(Command(commands=["webview"]))
+async def command_webview(message: Message, base_url: str):
+    await message.answer(
+        "Good. Now you can try to send it via Webview",
+        reply_markup=InlineKeyboardMarkup(
+            inline_keyboard=[
+                [
+                    InlineKeyboardButton(
+                        text="Open Webview", web_app=WebAppInfo(url=f"{base_url}/demo")
+                    )
+                ]
+            ]
+        ),
+    )
+
+
+@my_router.message(~F.message.via_bot)  # Echo to all messages except messages via bot
+async def echo_all(message: Message, base_url: str):
+    await message.answer(
+        "Test webview",
+        reply_markup=InlineKeyboardMarkup(
+            inline_keyboard=[
+                [InlineKeyboardButton(text="Open", web_app=WebAppInfo(url=f"{base_url}/demo"))]
+            ]
+        ),
+    )