Migration guide 2.x -> 3.0 (#1143)

* Initial commit for docs cleanup

* Update migration guide

* More docs

* Added changes description

* Small fixes

docs/api/enums/index.rst

@@ -1,3 +1,5 @@
+.. _enums:
+
 #####
 Enums
 #####

docs/api/session/custom_server.rst

@@ -1,14 +1,14 @@
 Use Custom API server
 =====================
 
-.. autoclass:: aiogram.client.telegram.TelegramAPIServer
-    :members:
-
 For example, if you want to use self-hosted API server:
 
-.. code-block:: python3
+.. code-block:: python
 
     session = AiohttpSession(
         api=TelegramAPIServer.from_base('http://localhost:8082')
     )
     bot = Bot(..., session=session)
+
+.. autoclass:: aiogram.client.telegram.TelegramAPIServer
+    :members:

docs/api/session/index.rst

@@ -8,3 +8,4 @@ Client sessions is used for interacting with API server.
     custom_server
     base
     aiohttp
+    middleware

docs/api/session/middleware.rst

@@ -0,0 +1,75 @@
+##########################
+Client session middlewares
+##########################
+
+In some cases you may want to add some middlewares to the client session to customize the behavior of the client.
+
+Some useful cases that is:
+
+- Log the outgoing requests
+- Customize the request parameters
+- Handle rate limiting errors and retry the request
+- others ...
+
+So, you can do it using client session middlewares.
+A client session middleware is a function (or callable class) that receives the request and the next middleware to call.
+The middleware can modify the request and then call the next middleware to continue the request processing.
+
+How to register client session middleware?
+==========================================
+
+Register using register method
+------------------------------
+
+.. code-block:: python
+
+    bot.session.middleware(RequestLogging(ignore_methods=[GetUpdates]))
+
+Register using decorator
+------------------------
+
+.. code-block:: python
+
+    @bot.session.middleware()
+    async def my_middleware(
+        make_request: NextRequestMiddlewareType[TelegramType],
+        bot: "Bot",
+        method: TelegramMethod[TelegramType],
+    ) -> Response[TelegramType]:
+        # do something with request
+        return await make_request(bot, method)
+
+
+Example
+=======
+
+Class based session middleware
+------------------------------
+
+.. literalinclude:: ../../../aiogram/client/session/middlewares/request_logging.py
+    :lines: 16-
+    :language: python
+    :linenos:
+
+.. note::
+
+    this middlewware is already implemented inside aiogram, so, if you want to use it you can
+    just import it :code:`from aiogram.client.session.middlewares.request_logging import RequestLogging`
+
+
+Function based session middleware
+---------------------------------
+
+.. code-block:: python
+
+    async def __call__(
+        self,
+        make_request: NextRequestMiddlewareType[TelegramType],
+        bot: "Bot",
+        method: TelegramMethod[TelegramType],
+    ) -> Response[TelegramType]:
+        try:
+            # do something with request
+            return await make_request(bot, method)
+        finally:
+            # do something after request

docs/api/types/error_event.rst

@@ -1,10 +0,0 @@
-##########
-ErrorEvent
-##########
-
-
-.. automodule:: aiogram.types.error_event
-    :members:
-    :member-order: bysource
-    :undoc-members: True
-    :exclude-members: model_config,model_fields