resource: fix resource from model lookup now uses hierarchy correctly

It keeps traversing the object hierarchy until it finds one that isn't None.

If it gets exhausted (that shouldn't happen) it just returns Resource, but the last loop iteration should already do that as it hits "top".

Also add some docstrings to resource.py

Fixes #38

src/sambal/resources/resource.py

@@ -1,23 +1,48 @@
+from typing import Type
+
 from samba.domain.models import Model
 
-# A lookup table object_class to Resource.
+# A lookup table object_class to Resource class.
 RESOURCES = {}
 
 
 class ResourceMeta(type):
+    """Resource metaclass automatically populates the RESOURCES lookup table.
+
+    This lookup table is used by resource_for_model to find a resource for
+    the given object class.
+    """
+
     def __new__(mcls, name, bases, namespace, **kwargs):
         cls = super().__new__(mcls, name, bases, namespace, **kwargs)
         RESOURCES[cls.model.get_object_class()] = cls
         return cls
 
 
 class Resource(dict, metaclass=ResourceMeta):
+    """Resource base class represents the object class "top" or the base Model.
+
+    Create specific resources for each Model subclass inheriting of Resource.
+    """
+
     model = Model
 
     def __init__(self, request, obj):
+        """The constructor for non-container objects.
+
+        Container objects need to fetch the children as well, regular objects
+        don't have to do this and are simply an update of the current object.
+        """
         super().__init__()
         self.update(obj.as_dict())
 
     @staticmethod
-    def resource_for_model(model):
-        return RESOURCES.get(model.get_object_class(), Resource)
+    def resource_for_model(obj: Model) -> Type["Resource"]:
+        """Traverse object hierarchy in reverse finding the closest Resource"""
+        object_hierarchy = reversed(obj.object_class)
+
+        for object_class in object_hierarchy:
+            if resource := RESOURCES.get(object_class):
+                return resource
+
+        return Resource