fixes serializer types and test

pydase dicts can only have stringed keys. This is now reflected in the serializer, as well.

tests/utils/serialization/test_serializer.py

@@ -400,7 +400,7 @@ def test_dict_serialization() -> None:
 
     test_dict = {
         "int_key": 1,
-        1.0: 1.0,
+        "1.0": 1.0,
         "bool_key": True,
         "Quantity_key": 1.0 * u.units.s,
         "DataService_key": MyClass(),
@@ -442,8 +442,8 @@ def test_dict_serialization() -> None:
                 "type": "bool",
                 "value": True,
             },
-            1.0: {
-                "full_access_path": "[1.0]",
+            "1.0": {
+                "full_access_path": '["1.0"]',
                 "doc": None,
                 "readonly": False,
                 "type": "float",