Feat skeleton build task

[drewbo]

Changes proposed in this pull request:

Extreme WIP (but functional) PR which implements the following items from the acceptance criteria

• Create a build task queue
• Run build task when a site build starts and when site build completes, depending on user/task config
• Run task from worker thread
• Update tasks queue with new status
• On task complete, save task artifact and complete tasks queue with finish status.

I've also added a "hidden admin page" at /tasks which shows some build task information. The build task does run code, but currently it's fully encapsulated in the worker, rather than running a CF task. I have a number of problems with the current architecture and would love advice on proceeding:

• As we've identified previously, the project has an odd mix of object-oriented vs functional programming throughout. The place it is most obvious here is the faux-instance methods enqueue (previously existing) and startBuildTask (added).
• As written, the tasks are all implemented as worker code only, rather than CF tasks. They also have implied customs with no way to enforce them (function arguments and artifacts location)
• Because the worker tasks have access to the DB directly, they don't necessary need to use the status endpoint but I've included it as an example. Do we want to have some tasks available as worker code only or should they all be CF tasks?

security considerations

New non-user enforced endpoint is added for status reporting (uses secret token to validate responses)

[apburnes]

Mostly looking for your thoughts on different options for kicking off the build tasks. Once we test out running jobs on a worker, cf task, or third party service, we'll have a better idea of how we want the job processor interface to function. We may want to lean more on bullmq's API for managing the job lifecycle but this is a great start. Awesome work.

[drewbo]

@apburnes updated in response to your feedback:

• I added the Promise.allSettled to the tasks but right now there isn't a return value, seems okay just noting
• it's currently not started the "build complete" build task: still looking into that

[apburnes]

@drewbo looks good so far.

[drewbo]

This is ready to go again, in conjunction with cloud-gov/pages-cf-build-tasks#1. It contains API tests but nothing for the CF API call to the tasks endpoint; happy to add that before final review.

Also because this is a large feature, I'm available to demo or add more docs as needed.

[apburnes]

👏