date/time from EXIF API

[TanyaStere42]

Context

When uploading images as part of an encounter, users should be able to leverage the information from the photographs to simplify their data entry experience. We want users to be able to see a list of date/times from their photos, so we need an API that pulls that information. (needed for #793)

Requirements

Non-Functional Requirement

• PR needs to branch off of feature branch: submission_page

Functional Requirement

• GET API
• 200: list of datetimes from exif date created for one or more submitted images
• 400: "could not parse exif date created" if error parsing or if no exif date created is on image

[naknomum]

maybe worth investigating submit.jsp and its use of javascript/exif.js through exifFindLatLon() (this would be frontend-only implementation).

otherwise could be BE api that can return MediaAssetMetadata on already-uploaded files (from #750)