Added current user filter to assignee dropdown

Adds an option in the assignee filter dropdown that allows the user to
filter issues that are assigned to them

Closes #26882

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

@@ -47,6 +47,10 @@
               %li.filter-dropdown-item{ 'data-value' => 'none' }
                 %button.btn.btn-link
                   No Assignee
+              - if current_user
+                %li.filter-dropdown-item{ 'data-value' => current_user.to_reference }
+                  %button.btn.btn-link
+                    Assigned to me
               %li.divider
             %ul.filter-dropdown{ 'data-dynamic' => true, 'data-dropdown' => true }
               %li.filter-dropdown-item

spec/features/issues/filtered_search/dropdown_assignee_spec.rb

@@ -43,6 +43,14 @@ describe 'Dropdown assignee', js: true, feature: true do
       expect(page).to have_css(js_dropdown_assignee, visible: true)
     end
 
+    it 'shows assigned to me link' do
+      filtered_search.set('assignee:')
+
+      page.within js_dropdown_assignee do
+        expect(page).to have_content('Assigned to me')
+      end
+    end
+
     it 'closes when the search bar is unfocused' do
       find('body').click()
 
@@ -121,6 +129,14 @@ describe 'Dropdown assignee', js: true, feature: true do
       filtered_search.set('assignee:')
     end
 
+    it 'filters by current user' do
+      page.within js_dropdown_assignee do
+        click_button 'Assigned to me'
+      end
+
+      expect(filtered_search.value).to eq("assignee:#{user.to_reference}")
+    end
+
     it 'fills in the assignee username when the assignee has not been filtered' do
       click_assignee(user_jacob.name)