Update build-task enqueu function to kick off tasks via a queue-job convention

[apburnes]

Update the creation of a build task queue job by using the queue-job convention.

Acceptance Criteria

• [ ] Create a startBuildTask function in ./api/queue-job to add a new build task job
• [ ] Update the build-task model enqueue method to use the startBuildTask
• [ ] Move db query logic and message creation to the build task job processor