Propose batch from pre-constructed jobs

[hkethi002]

Fixes #940

Changes

• New Endpoint: POST /batch/jobs with a list of jobs, jobs: [{...}, {...}, ...], in the payload
• The job maps from the payload are stored in batch.proposal.preconstructed_jobs in mongo
• Jobs are validated on proposal for gear manifest, inputs, config, and permissions
• On batch run, the jobs then follow the normal job cycle

Review Checklist

• Tests were added to cover all code changes
• Documentation was added / updated
• Code and tests follow standards in CONTRIBUTING.md

[codecov-io]

Codecov Report

Merging #1069 into master will increase coverage by 0.04%.
The diff coverage is 97.5%.

@@            Coverage Diff             @@
##           master    #1069      +/-   ##
==========================================
+ Coverage    90.8%   90.85%   +0.04%     
==========================================
  Files          50       50              
  Lines        7029     7063      +34     
==========================================
+ Hits         6383     6417      +34     
  Misses        646      646

[AshleyAncona]

@nagem and @kofalt this is ready for review

[kofalt]

Break these two branches out into different functions, and call them from here.

[kofalt]

Please do not change this function signature. Instead, revert changes to this function, then remove job.insert() to make it consistent with the original documentation. Then check usage of enqueue_job to see who will need job.insert() added after calling.

[kofalt]

[kofalt]

Notably, this PR is a lot easier to read when using w=1.