Simplify end-to-end test setup

Besides that, this commit tries to fix an issue that happens on
staging, where user fabrication via API doesn't work, and it may
be due to the usage of let(:user) since other tests using
User.fabricate_via_api! don't use it in a let declaration.

In this commit I'm moving the user fabrication to the before block
and exposing it as an instance variable @user, so that it can be
used in the test itself.

Also, I have removed unnecessary steps that makes the test slower.

qa/qa/specs/features/browser_ui/2_plan/issue/mentions_spec.rb

@@ -3,29 +3,12 @@
 module QA
   context 'Plan', :smoke do
     describe 'mention' do
-      let(:user) do
-        Resource::User.fabricate_via_api! do |user|
-          user.name = "bob"
-          user.password = "1234test"
-        end
-      end
-
       before do
-        QA::Runtime::Env.personal_access_token = QA::Runtime::Env.admin_personal_access_token
-
-        unless QA::Runtime::Env.personal_access_token
-          Runtime::Browser.visit(:gitlab, Page::Main::Login)
-          Page::Main::Login.perform(&:sign_in_using_admin_credentials)
-        end
-
-        QA::Runtime::Env.personal_access_token = nil
-
-        Page::Main::Menu.perform(&:sign_out) if Page::Main::Menu.perform { |p| p.has_personal_area?(wait: 0) }
-
         Runtime::Browser.visit(:gitlab, Page::Main::Login)
-
         Page::Main::Login.perform(&:sign_in_using_credentials)
 
+        @user = Resource::User.fabricate_or_use(Runtime::Env.gitlab_qa_username_1, Runtime::Env.gitlab_qa_password_1)
+
         project = Resource::Project.fabricate_via_api! do |resource|
           resource.name = 'project-to-test-mention'
         end
@@ -33,7 +16,7 @@ module QA
 
         Page::Project::Show.perform(&:go_to_members_settings)
         Page::Project::Settings::Members.perform do |members|
-          members.add_member(user.username)
+          members.add_member(@user.username)
         end
 
         issue = Resource::Issue.fabricate_via_api! do |issue|
@@ -45,7 +28,7 @@ module QA
 
       it 'user mentions another user in an issue' do
         Page::Project::Issue::Show.perform do |show|
-          at_username = "@#{user.username}"
+          at_username = "@#{@user.username}"
 
           show.select_all_activities_filter
           show.comment(at_username)