add docs, provide check if Config is a class, ignore dynamic bases for mypy

ormar/models/metaclass.py

@@ -1,3 +1,4 @@
+import inspect
 from typing import (
     Any,
     Dict,
@@ -552,12 +553,20 @@ class ModelMetaclass(pydantic.main.ModelMetaclass):
         :param attrs: class namespace
         :type attrs: Dict
         """
+        DefaultConfig = get_pydantic_base_orm_config()
         if "Config" in attrs:
-            class Config(attrs["Config"], get_pydantic_base_orm_config()):
+            ProvidedConfig = attrs["Config"]
+            if not inspect.isclass(ProvidedConfig):
+                raise ModelDefinitionError(
+                    f"Config provided for class {name} has to be a class."
+                )
+
+            class Config(ProvidedConfig, DefaultConfig):  # type: ignore
                 pass
+
             attrs["Config"] = Config
         else:
-            attrs["Config"] = get_pydantic_base_orm_config()
+            attrs["Config"] = DefaultConfig
 
         attrs["__name__"] = name
         attrs, model_fields = extract_annotations_and_default_vals(attrs)