feat: Add a view for mentions (#3505)

- Added a new table mentions for saving user mentions
- Added a filter conversation_type in the API
- Added a view to see the mentions

app/javascript/dashboard/components/specs/SidemenuIcon.spec.js

@@ -1,9 +1,9 @@
-import { mount } from '@vue/test-utils';
+import { shallowMount } from '@vue/test-utils';
 import SidemenuIcon from '../SidemenuIcon';
 
 describe('SidemenuIcon', () => {
   test('matches snapshot', () => {
-    const wrapper = mount(SidemenuIcon);
+    const wrapper = shallowMount(SidemenuIcon);
     expect(wrapper.vm).toBeTruthy();
     expect(wrapper.element).toMatchSnapshot();
   });