Implement integration backend tests for the product code

[googollee]

It'd be better to have integrated tests with the release image. Tests should cover main functions, like:

• Scan job
• Convert RAW

Add more please.

[kkovaletp]

Thanks for submitting the issue. I'll try to expand the list of tests:

• Scan job:
  • Scan a few examples of non-RAW images in the most popular formats
  • Scan a few examples of videos in the most popular formats
  • Scan a few examples of RAW images in the most popular formats
• CRUD + Merge operations for faces
• Paginated load of thumbnails on UI request for Timeline and Albums
• Sequential load of high-res images and videos on UI request in Viewer
• Load info about several images and videos
• Filtering and grouping media for Maps UI

Of course, these areas might be covered iteratively over time. There is no urgent need to prepare all of them in 1 or several PRs during a short time period