Data exports

[nciemniak]

Data Exports functionality is responsible for:

• Generating transcription data files and saving them to Azure Blob Storage upon transcription approval. this includes a raw data file (.json), a consensus text file (.txt), a metadata file (.csv), and a line metadata file (.csv)
• Removing transcription data files from storage if transcription is unapproved
• Downloading all transcription files pertaining to a requested project, workflow, group, or single transcription, zipping the files, and sending them to the user
• Generating a single csv file containing the metadata for all transcriptions included in the collection (handled by the AggregateMetadataFileGenerator class), which is included in the zip file

[zwolf]

The very last thing I'll say on this is that I think it would be better form to mock the file system interactions rather than actually building them. This is potentially premature optimization but I want to flag it and maybe create and issue to explore alternatives to disk i/o for tests.

Not blocking, nice work.