Add belongs_to as DSL alias to has_one

Author: Olle Jonsson

lib/jsonapi/resource.rb

@@ -429,6 +429,7 @@ def relationship(*attrs)
       def has_one(*attrs)
         _add_relationship(Relationship::ToOne, *attrs)
       end
+      alias_method :belongs_to, :has_one
 
       def has_many(*attrs)
         _add_relationship(Relationship::ToMany, *attrs)

test/unit/jsonapi_request/jsonapi_request_test.rb

@@ -4,7 +4,7 @@ class CatResource < JSONAPI::Resource
   attribute :name
   attribute :breed
 
-  has_one :mother, class_name: 'Cat'
+  belongs_to :mother, class_name: 'Cat'
   has_one :father, class_name: 'Cat'
 
   filters :name