Teach BorderBox component a list_arguments param

Allows additional customization of the rendered `<ul>` by supporting
system arguments.

Closes primer#3820

Author: myabc

app/components/primer/beta/border_box.rb

@@ -71,8 +71,9 @@ class BorderBox < Primer::Component
       }
 
       # @param padding [Symbol] <%= one_of(Primer::Beta::BorderBox::PADDING_MAPPINGS.keys) %>
+      # @param list_arguments [Hash] <%= link_to_system_arguments_docs %>
       # @param system_arguments [Hash] <%= link_to_system_arguments_docs %>
-      def initialize(padding: DEFAULT_PADDING, **system_arguments)
+      def initialize(padding: DEFAULT_PADDING, list_arguments: {}, **system_arguments)
         list_id = system_arguments.delete(:list_id)
 
         @system_arguments = deny_tag_argument(**system_arguments)
@@ -84,9 +85,10 @@ def initialize(padding: DEFAULT_PADDING, **system_arguments)
         )
 
         @system_arguments[:system_arguments_denylist] = { [:p, :pt, :pb, :pr, :pl] => PADDING_SUGGESTION }
-        @list_arguments = { tag: :ul }
+        @list_arguments = deny_tag_argument(**list_arguments)
+        @list_arguments[:tag] = :ul
         @list_arguments[:id] = list_id if list_id
-        @list_arguments[:classes] = "Box-list"
+        @list_arguments[:classes] = class_names("Box-list", @list_arguments[:classes])
       end
 
       def render?
@@ -98,9 +100,10 @@ def render?
       def before_render
         return unless header
 
-        @list_arguments[:aria] = {
-          labelledby: header.id
-        }
+        @list_arguments[:aria] = merge_aria(
+          @list_arguments,
+          { aria: { labelledby: header.id } }
+        )
       end
     end
   end

test/components/beta/border_box_test.rb

@@ -33,6 +33,28 @@ def test_labels_list_with_header
     assert_selector "ul[aria-labelledby='#{id}']"
   end
 
+  def test_renders_list_with_list_arguments
+    render_inline(Primer::Beta::BorderBox.new(list_arguments: { id: "fake-tbody", role: "rowgroup" })) do |component|
+      component.with_row { "Row" }
+    end
+
+    assert_selector "ul#fake-tbody"
+    assert_selector 'ul[role="rowgroup"]'
+  end
+
+  def test_labels_list_with_header_and_additional_label
+    render_inline(Primer::Beta::BorderBox.new(list_arguments: { aria: { labelledby: "my-footer" } })) do |component|
+      component.with_header { "Header" }
+      component.with_row { "Row" }
+      component.with_footer(id: "my-footer") { "Footer" }
+    end
+
+    header_id = page.find_css(".Box-header").first[:id]
+    footer_id = page.find_css(".Box-footer").first[:id]
+    assert_selector "ul[aria-labelledby*='#{header_id}']"
+    assert_selector "ul[aria-labelledby*='#{footer_id}']"
+  end
+
   def test_renders_body
     render_inline(Primer::Beta::BorderBox.new) do |component|
       component.with_body { "Body" }