Add full_name property to Contact and corresponding tests (#1758)

* Add full_name property to Contact and corresponding tests

* Add brief description of changes

tests/test_api/test_types/test_contact.py

@@ -0,0 +1,20 @@
+import pytest
+
+from aiogram.types import Contact
+
+
+class TestContact:
+    @pytest.mark.parametrize(
+        "first,last,result",
+        [
+            ["User", None, "User"],
+            ["", None, ""],
+            [" ", None, " "],
+            ["User", "Name", "User Name"],
+            ["User", " ", "User  "],
+            [" ", " ", "   "],
+        ],
+    )
+    def test_full_name(self, first: str, last: str, result: bool):
+        contact = Contact(phone_number="911", first_name=first, last_name=last)
+        assert contact.full_name == result