Add job_urls field to post_jobs response

[jtherrmann]

See #1273

This PR adds a job_urls field to the POST /jobs response, so that we do not have to manually concatenate the API domain name and the job ID for every job when submitting jobs via the API. Here is an example response:

{
  "job_urls": [
    "https://hyp3-enterprise-test.asf.alaska.edu/jobs/13d6eac4-b4e6-4281-951e-d79d356693bf",
    "https://hyp3-enterprise-test.asf.alaska.edu/jobs/1693d659-6bba-495e-9332-b68dcd753e57",
    "https://hyp3-enterprise-test.asf.alaska.edu/jobs/ac2c7a9f-d278-4673-89b1-bf7faa7118c3"
  ],
  "jobs": [...],
  "validate_only": false
}

This makes it much easier to open and keep track of a batch of submitted test jobs, for example, or to comment the list of URLs in an open task/issue.

TODO:

• Address TODOs in code.

[jhkennedy]

@jtherrmann ooh, this could be handy.

I wonder if we should also (instead?) add a job_url to each job -- when you do searches for multiple jobs (e.g., by name) you'd have URLs to open that specific job.

[jtherrmann]

@jhkennedy I think I'd like both. My only dilemma with adding a job_url field to each job dict is whether to store it as a field in the database, or insert it dynamically when returning the job via the API.

[jtherrmann]

I don't have as much need for this feature since we added the search-for-other-users'-jobs feature.