Add Document Encryption Service for Doc Escrow

[Sgtpluck]

🎫 Ticket

Link to the relevant ticket:
Add Document Encryption Service for Doc Escrow

🛠 Summary of changes

This change adds an EncryptedDocStorage service that will be used for Doc Escrow.

• encrypts the front and back images of a document
• stores the images locally by default
• returns the image UUIDs and the encryption key

Open questions:
This implementation stole liberally from @jmhooper's initial implementation of this service. It currently relies on two images being passed in. Do we think that will always be the case? Is it possible that there might be single images (like a selfie?)

I am wondering if this updated implementation should:

• Only accept a single image so that the caller of this method has to call it multiple times for each image they want encrypted, and each image has its own encryption key, OR;
• Accept an array of images and then loop over them, and return all the uuids with a single encryption key, OR;
• Make the same assumptions the first implementation made about there always being a front/back image.

I think I like the first option best, as it makes less assumptions, but does mean multiple encryption keys. Would love to hear other thoughts!

[zachmargolis]

• Only accept a single image so that the caller of this method has to call it multiple times for each image they want encrypted, and each image has its own encryption key, OR;

I also vote for one image at a time, I think it would simplify the structure and allow for flexibility across multiple flows (with and without selfie)

[mitchellhenke]

I lean towards the first option in that documents should be stored and referenced individually

[zachmargolis]

another approach to cleanup and writing files to disk would be to make the whole example use a tmpdir, like we do here. We could update the class to take an optional dir argument and pass the path in here, the default value would be the Rails.root.join('tmp') like have it now

identity-idp/spec/lib/i18n_flat_yml_backend_spec.rb

Lines 36 to 41 in 0b303ab

	around do |ex|
	Dir.mktmpdir('/locales') do |dir|
	@tmpdir = dir
	ex.run
	end
	end

[Sgtpluck]

i considered a couple different approaches to cleanup, but since it was just two specs in different spec files, it seemed fine to just inline it for now. will definitely consider other approaches as we extend it. (unless you feel very strongly about it, then i can update it now!)

[zachmargolis]

Not that strongly!

[jmhooper]

I will note the passports only have a single image. I don't have a strong opinion about how we handle a single image or 3 images but I think we do need to support it.

[jmhooper]

This does look familiar to me. I feel good about this approach.