Implement data integrity unit tests

[x] Every contribution document should have reference metadata
[ ] Every contribution should have contribution metadata (id, version, is_activated, is_validated, etc.)
[ ] Every contribution should have a data file in S3 with the same contribution metadata
[ ] Each child document from the contribution should be indexed
[ ] Each child document should have the same contribution metadata as the contribution document
[ ] Each child document should include the raw data

earthref / MagIC