refactor and cleanup - drop of resolving relation names as not fully proper, extract mixins from modelproxy to be more maintainable, add some docstrings

ormar/relations/utils.py

@@ -14,16 +14,11 @@ def get_relations_sides_and_names(
     child: "Model",
     child_name: str,
     virtual: bool,
+    relation_name: str,
 ) -> Tuple["Model", "Model", str, str]:
     to_name = to_field.name
     if issubclass(to_field, ManyToManyField):
-        child_name, to_name = (
-            to_field.related_name
-            or child.resolve_relation_name(
-                parent, to_field.through, explicit_multi=True
-            ),
-            to_name,
-        )
+        child_name = to_field.related_name or child.get_name() + "s"
         child = proxy(child)
     elif virtual:
         child_name, to_name = to_name, child_name or child.get_name()