Investigate and fix issue with the caching of files from backblaze

Update 23.06.21

Backblaze seems to fix the issue. After setting empty cache settings to the Backblaze bucket problem disappeared.

Description

When the browser attempts to fetch any not existing file, CDN returns CORS error and browser caches the response. Next time, even if file has been uploaded, browser returns cached error, and there's no way to retrieve the file.

Acceptance criteria

• Try to alter cache-control headers of the CDN, and in case of no success, contact Backblaze Support.
• Get rid of random string dirty fix for fetching files from Backblaze

QA

• Deploy Web Verification App and Iframe

• Send an email via the Add-in or Extension

• Immediately start verifying it via the Add-in/Extension interface and Web Verification App to encounter "Pending" state

• Wait some time and verify again. Apps must verify statuses after the time passed.

  The wrong behavior would be sticking to the pending state indefinitely