fix: Static gzip Media Signature

[jshlbrd]

Description

• Adds a static media signature for application/x-gzip

Motivation and Context

There is an occasional media identification bug when retrieving compressed CloudTrail files from AWS S3 -- http.DetectContentType incorrectly identifies the media type as application/vnd.ms-fontobject. The bug is rare (at Brex we process more than 100k compressed CloudTrail files every day and we see the bug, at most, once every few months) but it needs to be fixed because it results in data loss.

How Has This Been Tested?

The fix was integration tested with a CloudTrail file known to trigger the false match.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[shellcromancer]

Looks good! If we have a small, sanitized file it would be great to have a test recognizing the content-type.

[jshlbrd]

Looks good! If we have a small, sanitized file it would be great to have a test recognizing the content-type.

We have test coverage for the function that correctly identifies gzip, but a public test file for the fix itself probably isn't a good idea -- it can't be sanitized without changing the MIME type (gunzip -> gzip), which would most likely corrupt the test.

That mentioned, we can host it internally for our own integration tests.