Add a database record of photos taken in the field

[spwoodcock]

Is your feature request related to a problem? Please describe.

• The images taken are stored in the ODK Collect database submission_attachments table as blobs.
• This is fine to extracting submission as a .zip and providing to the user, but it's not good enough for usage in a UI.
• We need to store images in S3 and keep a record in the FMTM database.

Describe the solution you'd like

• Add a new db table called submission_photos with fields for the associated task id, entity id, s3_path.
• Create migrations for this.
• Follow on in Extract user photos from submissions and make available via S3 #1701