Add optional default_authorize callback

This allows setting the `authorize: ...` value for all fields if none was set.

This allows for an easier adoption for APIs that might previously not
have any role-based authorization. Defaulting to their default role,
for instance, :admin, and only adding `authorize: ...` where authorization
can be relaxed.

lib/authorization.ex

@@ -30,6 +30,8 @@ defmodule Rajska.Authorization do
 
   @callback context_user_authorized?(context, scoped_struct, rule) :: boolean()
 
+  @callback default_authorize(context, scoped_struct) :: role() | nil
+
   @optional_callbacks get_current_user: 1,
                       get_ip: 1,
                       get_user_role: 1,
@@ -38,5 +40,6 @@ defmodule Rajska.Authorization do
                       has_user_access?: 3,
                       unauthorized_message: 1,
                       context_role_authorized?: 2,
-                      context_user_authorized?: 3
+                      context_user_authorized?: 3,
+                      default_authorize: 2
 end

lib/middlewares/object_authorization.ex

@@ -88,10 +88,17 @@ defmodule Rajska.ObjectAuthorization do
   defp authorize_object(object, fields, resolution) do
     object
     |> Type.meta(:authorize)
+    |> default_authorize(resolution.context, object)
     |> authorized?(resolution.context, object)
     |> put_result(fields, resolution, object)
   end
 
+  defp default_authorize(nil, context, object) do
+    Rajska.apply_auth_mod(context, :default_authorize, [context, object])
+  end
+
+  defp default_authorize(authorize, _context, _object), do: authorize
+
   defp authorized?(nil, _, object), do: raise "No meta authorize defined for object #{inspect object.identifier}"
 
   defp authorized?(permission, context, _object) do

lib/rajska.ex

@@ -65,7 +65,8 @@ defmodule Rajska do
   defmacro __using__(opts \\ []) do
     super_role = Keyword.get(opts, :super_role, :admin)
     valid_roles = Keyword.get(opts, :valid_roles, [super_role])
-    default_rule =  Keyword.get(opts, :default_rule, :default)
+    default_rule = Keyword.get(opts, :default_rule, :default)
+    default_authorize = Keyword.get(opts, :default_authorize, nil)
 
     quote do
       @behaviour Authorization
@@ -130,6 +131,8 @@ defmodule Rajska do
         |> get_current_user()
         |> has_user_access?(scoped_struct, rule)
       end
+
+      def default_authorize(_context, _object), do: unquote(default_authorize)
 
       defoverridable Authorization
     end