Feat/proxy cache debug

[utix]

Summary

Remove proxy cache headers from response if the kong debug is not set. Adding Miss/Hit, Age and cache key to answer shouldn't be the default behavior.

Full changelog

The following headers:

• X-Cache-Status
• X-Cache-Key
• Age

are now set only if the header kong-debug is set to 1

Refactor test to remove duplicated lines and use get, post and delete helpers instead of send