Fix WS connection hijack

[otherview]

Description

Hijack lets the caller take over the connection. This is needed in WS connections and was not implemented in the metrics new response writer.

This PR adds the Hijack method.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] New and existing E2E tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 62.58%. Comparing base (27e60e6) to head (5779eba).

Files	Patch %	Lines
api/metrics.go	0.00%	5 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #766 +/- ## ========================================== - Coverage 62.59% 62.58% -0.02% ========================================== Files 199 199 Lines 18093 18098 +5 ========================================== Hits 11326 11326 - Misses 5685 5690 +5 Partials 1082 1082 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.