Upload and view sample data for a Data Entity

[nateiam]

As a Herd OSS data publisher I want to upload a sample data file and make it available for users

See https://github.com/FINRAOS/herd/wiki/Publishing-Sample-Data for some details

Acceptance Criteria

• Data Publisher can pre-register Sample Data file by calling Sample Data Upload Initiate endpoint in Herd
• Data Publisher can place file in S3 location specified by Sample Data Upload Initiate
• Herd completes registration of Sample Data
• User can view and download Sample Data in Herd-UI
• Sample Data Upload Initiate and S3 upload steps are performed during sample data population in MDL CFT