WIP Attachments Fixes

[rootelement]

The challenge api should accept URLs, then stream out requests for those files.

Tasks

• Change the attachments object to be attachments not attachmentIds
• Change the validation on attachments, and attachment should be an {id: , url: }
  • If you post or PUT [{url}, {url}] with no id property It should create those entries with UUIDs
  • If you PUT with an ID, it should update the URL (if it's different)
• Add endpoint GET /v5/challenges/:uuid/attachments
• Add endpoint GET /v5/challenges/:uuid/attachments/:uuid to stream the file down to the user from S3
• Update the swagger
• Update the postman

[rootelement]

AV Scan Repo, if necessary:
#7 (comment)