Use helper method to set filtered search input attributes

The list of attributes for the filtered search input was getting long, so use a
helper method to fill that hash.

Also, for multiple issue assignees, a helper is more convenient because it would
allow EE to override the behavior if MIA is supported.

app/helpers/search_helper.rb

@@ -126,6 +126,18 @@ module SearchHelper
     search_path(options)
   end
+  def search_filter_input_options(type)
+    {
+      id: "filtered-search-#{type}",
+      placeholder: 'Search or filter results...',
+      data: {
+        'project-id' => @project.id,
+        'username-params' => @users.to_json(only: [:id, :username]),
+        'base-endpoint' => namespace_project_path(@project.namespace, @project)
+      }
+    }
+  end
+
   # Sanitize a HTML field for search display. Most tags are stripped out and the
   # maximum length is set to 200 characters.
   def search_md_sanitize(object, field)

app/views/shared/issuable/_search_bar.html.haml

@@ -23,7 +23,7 @@
             .scroll-container
               %ul.tokens-container.list-unstyled
                 %li.input-token
-                  %input.form-control.filtered-search{ id: "filtered-search-#{type.to_s}", placeholder: 'Search or filter results...', data: { 'project-id' => @project.id, 'username-params' => @users.to_json(only: [:id, :username]), 'base-endpoint' => namespace_project_path(@project.namespace, @project) } }
+                  %input.form-control.filtered-search{ search_filter_input_options(type) }
               = icon('filter')
             #js-dropdown-hint.filtered-search-input-dropdown-menu.dropdown-menu.hint-dropdown
               %ul{ data: { dropdown: true } }