Make datepicker_options optional

Default `datepicker_options` to `{}` in `SingleDatePickerInput`
(inherited by `RangeDatePickerInput`), and remove now-redundant
empty hash arguments from callsites.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: myabc

lib/primer/open_project/forms/dsl/single_date_picker_input.rb

@@ -35,7 +35,7 @@ module Dsl
         class SingleDatePickerInput < Primer::Forms::Dsl::TextFieldInput
           attr_reader :datepicker_options
 
-          def initialize(name:, label:, datepicker_options:, **system_arguments)
+          def initialize(name:, label:, datepicker_options: {}, **system_arguments)
             @datepicker_options = derive_datepicker_options(datepicker_options)
 
             super(name:, label:, **system_arguments)

modules/backlogs/app/forms/backlogs/backlog_header_form.rb

@@ -48,16 +48,14 @@ class BacklogHeaderForm < ApplicationForm
           label: attribute_name(:start_date),
           placeholder: attribute_name(:start_date),
           visually_hide_label: true,
-          leading_visual: { icon: :calendar },
-          datepicker_options: {}
+          leading_visual: { icon: :calendar }
         )
         dates.single_date_picker(
           name: :effective_date,
           label: attribute_name(:effective_date),
           placeholder: attribute_name(:effective_date),
           visually_hide_label: true,
-          leading_visual: { icon: :calendar },
-          datepicker_options: {}
+          leading_visual: { icon: :calendar }
         )
       end
 

spec/lib/primer/open_project/forms/dsl/input_methods_spec.rb

@@ -226,14 +226,14 @@
     end
 
     describe "#single_date_picker" do
-      let(:field_group) { form_dsl.single_date_picker(name:, label:, datepicker_options: {}, **options) }
+      let(:field_group) { form_dsl.single_date_picker(name:, label:, **options) }
 
       include_examples "input class", Primer::OpenProject::Forms::Dsl::SingleDatePickerInput
       it_behaves_like "supporting help texts"
     end
 
     describe "#range_date_picker" do
-      let(:field_group) { form_dsl.range_date_picker(name:, label:, datepicker_options: {}, **options) }
+      let(:field_group) { form_dsl.range_date_picker(name:, label:, **options) }
 
       include_examples "input class", Primer::OpenProject::Forms::Dsl::RangeDatePickerInput
       it_behaves_like "supporting help texts"