Dev 3.x flat package (#961)

* Move packages

* Added changelog

* Update examples/echo_bot.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

* Rename `handler` -> `handlers`

* Update __init__.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

tests/test_fsm/test_context.py

@@ -0,0 +1,59 @@
+import pytest
+
+from aiogram.fsm.context import FSMContext
+from aiogram.fsm.storage.base import StorageKey
+from aiogram.fsm.storage.memory import MemoryStorage
+from tests.mocked_bot import MockedBot
+
+pytestmark = pytest.mark.asyncio
+
+
+@pytest.fixture()
+def state(bot: MockedBot):
+    storage = MemoryStorage()
+    key = StorageKey(user_id=42, chat_id=-42, bot_id=bot.id)
+    ctx = storage.storage[key]
+    ctx.state = "test"
+    ctx.data = {"foo": "bar"}
+    return FSMContext(bot=bot, storage=storage, key=key)
+
+
+class TestFSMContext:
+    async def test_address_mapping(self, bot: MockedBot):
+        storage = MemoryStorage()
+        ctx = storage.storage[StorageKey(chat_id=-42, user_id=42, bot_id=bot.id)]
+        ctx.state = "test"
+        ctx.data = {"foo": "bar"}
+        state = FSMContext(
+            bot=bot, storage=storage, key=StorageKey(chat_id=-42, user_id=42, bot_id=bot.id)
+        )
+        state2 = FSMContext(
+            bot=bot, storage=storage, key=StorageKey(chat_id=42, user_id=42, bot_id=bot.id)
+        )
+        state3 = FSMContext(
+            bot=bot, storage=storage, key=StorageKey(chat_id=69, user_id=69, bot_id=bot.id)
+        )
+
+        assert await state.get_state() == "test"
+        assert await state2.get_state() is None
+        assert await state3.get_state() is None
+
+        assert await state.get_data() == {"foo": "bar"}
+        assert await state2.get_data() == {}
+        assert await state3.get_data() == {}
+
+        await state2.set_state("experiments")
+        assert await state.get_state() == "test"
+        assert await state3.get_state() is None
+
+        await state3.set_data({"key": "value"})
+        assert await state2.get_data() == {}
+
+        await state.update_data({"key": "value"})
+        assert await state.get_data() == {"foo": "bar", "key": "value"}
+
+        await state.clear()
+        assert await state.get_state() is None
+        assert await state.get_data() == {}
+
+        assert await state2.get_state() == "experiments"