Add serializer keyword argument as an alias for resource

lib/alba/resource.rb

@@ -364,14 +364,16 @@ def attribute(name, **options, &block)
       # @param name [String, Symbol] name of the association, used as key when `key` param doesn't exist
       # @param condition [Proc, nil] a Proc to modify the association
       # @param resource [Class<Alba::Resource>, String, Proc, nil] representing resource for this association
+      # @param serializer [Class<Alba::Resource>, String, Proc, nil] alias for `resource`
       # @param key [String, Symbol, nil] used as key when given
       # @param params [Hash] params override for the association
       # @param options [Hash<Symbol, Proc>]
       # @option options [Proc] if a condition to decide if this association should be serialized
       # @param block [Block]
       # @return [void]
       # @see Alba::Association#initialize
-      def association(name, condition = nil, resource: nil, key: nil, params: {}, **options, &block)
+      def association(name, condition = nil, resource: nil, serializer: nil, key: nil, params: {}, **options, &block)
+        resource ||= serializer
         transformation = @_key_transformation_cascade ? @_transform_type : :none
         assoc = Association.new(
           name: name, condition: condition, resource: resource, params: params, nesting: nesting, key_transformation: transformation, helper: @_helper, &block

test/resource_test.rb

@@ -15,6 +15,7 @@ class BarResource
     include Alba::Resource
     attributes :id
   end
+  BarSerializer = BarResource
 
   class FooResource
     include Alba::Resource
@@ -111,7 +112,7 @@ class FooSerializer
     include Alba::Serializer
     root_key :foo
     attributes :id, :bar_size
-    many :bars, resource: BarResource
+    has_many :bars, serializer: BarSerializer
 
     def bar_size(foo)
       foo.bars.size