Support keyword arguments in iteration jobs

It's now more common to have jobs that take keyword arguments, like
`MyJob.perform_later(foo: "bar")`. But under the current implementation,
`build_enumerator` can only take them as a hash argument instead of
keyword arguments:

```ruby
def build_enumerator(params)
  foo = params[:foo]
  # ...
end
```

This commit fixes that by allowing keyword arguments to be passed to
`build_enumerator` and `each_iteration`.

lib/job-iteration/iteration.rb

@@ -107,8 +107,8 @@ def deserialize(job_data) # @private
       self.total_time = Float(job_data["total_time"] || 0.0)
     end
 
-    def perform(*params) # @private
-      interruptible_perform(*params)
+    def perform(*args, **kwargs) # @private
+      interruptible_perform(*args, **kwargs)
 
       nil
     end
@@ -128,12 +128,12 @@ def enumerator_builder
       JobIteration.enumerator_builder.new(self)
     end
 
-    def interruptible_perform(*arguments)
+    def interruptible_perform(*args, **kwargs)
       self.start_time = Time.now.utc
 
       enumerator = nil
       ActiveSupport::Notifications.instrument("build_enumerator.iteration", instrumentation_tags) do
-        enumerator = build_enumerator(*arguments, cursor: cursor_position)
+        enumerator = build_enumerator(*args, **kwargs, cursor: cursor_position)
       end
 
       unless enumerator
@@ -153,7 +153,7 @@ def interruptible_perform(*arguments)
       end
 
       completed = catch(:abort) do
-        iterate_with_enumerator(enumerator, arguments)
+        iterate_with_enumerator(enumerator, args, kwargs)
       end
 
       run_callbacks(:shutdown)
@@ -170,8 +170,9 @@ def interruptible_perform(*arguments)
       end
     end
 
-    def iterate_with_enumerator(enumerator, arguments)
-      arguments = arguments.dup.freeze
+    def iterate_with_enumerator(enumerator, args, kwargs)
+      args = args.dup.freeze
+      kwargs = kwargs.dup.freeze
       found_record = false
       @needs_reenqueue = false
 
@@ -183,7 +184,7 @@ def iterate_with_enumerator(enumerator, arguments)
         ActiveSupport::Notifications.instrument("each_iteration.iteration", tags) do
           found_record = true
           run_callbacks(:iterate) do
-            each_iteration(object_from_enumerator, *arguments)
+            each_iteration(object_from_enumerator, *args, **kwargs)
           end
           self.cursor_position = cursor_from_enumerator
         end

test/unit/active_job_iteration_test.rb

@@ -58,6 +58,16 @@ def each_iteration(_record, params)
       end
     end
 
+    class KwargsIterationJob < SimpleIterationJob
+      def build_enumerator(times:, cursor:)
+        enumerator_builder.build_times_enumerator(times, cursor: cursor)
+      end
+
+      def each_iteration(_record, times:)
+        self.class.records_performed << { times: times }
+      end
+    end
+
     class ActiveRecordIterationJob < SimpleIterationJob
       def build_enumerator(cursor:)
         enumerator_builder.active_record_on_records(
@@ -605,6 +615,12 @@ def test_passes_params_to_each_iteration
       assert_equal([params, params], ParamsIterationJob.records_performed)
     end
 
+    def test_passes_kwargs_to_each_iteration
+      KwargsIterationJob.perform_later(times: 3)
+      work_one_job
+      assert_equal([{ times: 3 }, { times: 3 }, { times: 3 }], KwargsIterationJob.records_performed)
+    end
+
     def test_passes_params_to_each_iteration_without_extra_information_on_interruption
       iterate_exact_times(1.times)
       params = { "walrus" => "yes", "morewalrus" => "si" }