[Feature] Update the /files endpoint to use new s3 buckets

[thetif]

Description and related issues

All of our files are currently stored in one s3 bucket. Bill has created new buckets to that we can separate out internal files that we want to share with the users (help docs) from the files that user upload.

User files should be uploaded to and retrieved from eapd-user-uploads Internal files should retrieved from eapd-interal-uploads

This task is done when…

• [ ] environment variables have been added for the new internal and user buckets for each environment (PREVIEW, STAGING, and PROD)
• [ ] files uploaded through the app go to the user bucket
• [ ] there is a way to distinguish between internal and externally uploaded file in the get request
• [ ] the get /files endpoint has been updated to handle requests for images and requires for internal files
• [ ] all links have been updated as appropriate
• [ ] requesting a help doc is successful
• [ ] requesting an image that has been updated is successful

	Given	When	Then
- [ ]	a request for a file	the file is a help doc or other internal doc	it is retrieved from the internal bucket
- [ ]	a require for a file	the file is an image uploaded through the app	it is retrieved from the internal bucket