Enhance Dataclass to unify decorator and class

The intention is to avoid having both the `dataclass` decorator and the `Dataclass` which feels a bit redundant.

superdesk/core/resources/model.py

@@ -65,27 +65,29 @@ def dataclass(*args, **kwargs):
     return pydataclass(*args, **kwargs, config=config)
 
 
-class Dataclass:
+class DataclassBase:
+    """Provides type-safe utility methods for Dataclass."""
+
     @model_serializer(mode="wrap")
-    def ser_model(self, nxt: SerializerFunctionWrapHandler):
-        aliased_fields = get_model_aliased_fields(self.__class__)
+    def ser_model(self, nxt: SerializerFunctionWrapHandler) -> dict[str, Any]:
+        """
+        Serialize the model, including extra fields not part of the schema.
+        """
         result = nxt(self)
 
         # Include extra fields that were not part of the schema for this class
         for key, value in self.__dict__.items():
-            if key not in result and key not in aliased_fields:
-                # If this key is not already in the result dictionary, and is not an aliased field
-                # then add it to the key, as an unknown field
+            if key not in result:
                 result[key] = value
 
         return result
 
     @classmethod
-    def from_dict(cls, values: dict[str, Any], **kwargs) -> Self:
+    def from_dict(cls: type[Self], values: dict[str, Any], **kwargs) -> Self:
         return RootModel.model_validate(values, **kwargs).root
 
     @classmethod
-    def from_json(cls, data: str | bytes | bytearray, **kwargs) -> Self:
+    def from_json(cls: type[Self], data: str | bytes | bytearray, **kwargs) -> Self:
         return RootModel.model_validate_json(data, **kwargs).root
 
     def to_dict(self, **kwargs) -> dict[str, Any]:
@@ -99,6 +101,28 @@ def to_json(self, **kwargs) -> str:
         return RootModel(self).model_dump_json(**default_params)
 
 
+class DataclassMeta(type):
+    """Metaclass to enhance Dataclass functionality."""
+
+    def __new__(cls, name, bases, dct):
+        custom_config = dct.pop("Config", {})
+
+        # merge with default configuration
+        config = deepcopy(default_model_config)
+        config.update(custom_config)
+
+        # create the class and apply the Pydantic dataclass decorator
+        new_cls = super().__new__(cls, name, bases, dct)
+        new_cls = pydataclass(new_cls, config=config)
+        return new_cls
+
+
+class Dataclass(DataclassBase, metaclass=DataclassMeta):
+    """Unified base class for dataclasses with Pydantic features."""
+
+    pass
+
+
 class ResourceModel(BaseModel):
     """Base ResourceModel class to be used for all registered resources"""