Add Job Status Updated Subscription

What does this MR do and why?

The purpose of this MR is to implement a subscription for front end views to be able to access real time updates on a job status. This will initially be used for real time updates on the job status icon in the job show page.

• ciJobStatusUpdated requires a global Ci::Build ID to initiate the subscription.
• the subscription is triggered when any transition event occurs on the job's status through an after commit hook on status updated
• the subscription payload is a Ci::JobType

References

Screenshots or screen recordings

How to set up and validate locally

Example Subscription query:

subscription jobStatusUpdated($jobId: CiBuildID!) {
  ciJobStatusUpdated(jobId: $jobId) {
    id
    status
  }
}

NOTE: You will need to set a jobId variable or you can pass it directly(see screenshots). The value required is a Ci:Build gid( ie. "gid://gitlab/Ci::Build/299"). You can also get the pipeline's formatted gid in the rails console by calling to_gid on an existing job/build.

1. Ensure you are logged into your local instance and navigate to the graphql explorer page (eg. http://gdk.test:3000/-/graphql-explorer or relace gdk.test:3000 to whatever your localhost is set to)
2. In your terminal start a rails console (bundle exec rails c)
3. In the console enable the feature flag Feature.enable(:ci_job_status_realtime)
4. In the console find a job/build you would like to use for testing and fetch the global id:

 job = Ci::Build.last 
 job.to_gid.uri.to_str #this is the string you will use for the $jobId variable in the graphql UI

5. Return to the graphql explorer and copy the query noted above ⬆️ before the steps
6. Set the jobId variable to the global id string you generated in the console in Step#3 (you can do this either directly in the subscription query or in the section below the query box that allows you to input variables:

{
  "jobId": "gid://gitlab/Ci::Build/???" #replace with the string you generated in the console
}

7. Press the play ▶️ in the graphql-explorer UI. The initial response should be nil because you are initiating/opening up the subscription. You should see this response:

{
  "data": {
    "ciJobStatusUpdated": null
  }
}

8. There are 2 ways to trigger the subscription from the rails console to test it out. Using the same job set earlier (job = Ci::Build.last) :

i. Triggering the subscription directly: GraphqlTriggers.ci_job_status_updated(job)

ii. Mocking a job state machine event with any valid action(depending on the current state of your job the actual status may update or not): job.cancel!

9. With either of the actions performed in Step#7 the subscription response should update with the values you set in the subscription and the data response should look something like:

{
  "data": {
    "ciJobStatusUpdated": {
      "id": 1234
      "status": "CANCELED",
    }
  }
}

Gotchas: If you are getting and unauthorized error make sure the user you are logged in as is authorized to read the build/project, probably best to be logged in as the root user.

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Related to #541146 (closed)