Add auto approve endpoint for protected studies

[dmgaldi]

Overview

• Added endpoint to approve eligible requests to access protected studies
• Request eligibility is determined by how much time has passed since the request was initiated
  • Datasets have a daysForApproval property that determines the duration threshold for approval

Testing

• Ran a dry-run, with actual DB update code turned off since we don't have a test account DB

Waiting for PR approval to actually test update code.

[Foxcapades]

Approved pending the changes noted by @ryanrdoherty