Add possibility to include router via string

tests/test_utils/test_imports.py

@@ -0,0 +1,29 @@
+import pytest
+
+import aiogram
+from aiogram.utils.imports import import_module
+
+
+class TestImports:
+    def test_bad_type(self):
+        with pytest.raises(ValueError, match=r"Target should be string not"):
+            import_module(42)
+
+    @pytest.mark.parametrize("value", ["module", "module:", ":attribute"])
+    def test_bad_format(self, value):
+        with pytest.raises(ValueError, match='must be in format "<module>:<attribute>"'):
+            import_module(value)
+
+    @pytest.mark.parametrize("value", ["module", "aiogram.KABOOM", "aiogram.KABOOM.TEST"])
+    def test_bad_value(self, value):
+        with pytest.raises(ValueError, match="Could not import module"):
+            import_module(f"{value}:attribute")
+
+    def test_has_no_attribute(self):
+        with pytest.raises(ValueError, match="has no attribute"):
+            import_module("aiogram:KABOOM")
+
+    def test_imported(self):
+        value = import_module("aiogram:__version__")
+        isinstance(value, str)
+        assert value == aiogram.__version__