feat: Update API for contact avatar (#4719)

Added the ability to update the contact's avatar via API and Dashboard.

- Contact create and update APIs can now accept avatar attachment parameters [form data].
- Contact create and update endpoints can now accept the avatar_url parameter.[json]
- API endpoint to remove a contact avatar.
- Updated Contact create/edit UI components with avatar support

Fixes: #3428

app/javascript/dashboard/api/contacts.js

@@ -71,6 +71,10 @@ class ContactAPI extends ApiClient {
       custom_attributes: customAttributes,
     });
   }
+
+  destroyAvatar(contactId) {
+    return axios.delete(`${this.url}/${contactId}/avatar`);
+  }
 }
 
 export default new ContactAPI();