Chatops is not updating the `User#last_activity_on` which means that people only using chatops become inactive

Problem

As discussed internally in Slack, we enabled deactivation of dormant accounts on ops.gitlab.net and many people that have an account on ops.gitlab.net purely so they can access chatops were deactivated because their chatops usage is not updating User#last_activity_on.

Solution

Whenever a user issues a chatops command we should trigger Users::ActivityService as we do in other places where a user triggers some activity. There were the following proposals:

1. ChatName#update_last_used_at
2. Gitlab::Chat::Command#create_pipeline

The Users::ActivityService is also usually updated at a very high level in our code though like lib/api/api.rb and app/controllers/graphql_controller.rb so maybe there is another entry point in our application that is missing this.