Prometheus: Add POST support to client (#60243)
* Prometheus: Add POST support to client
* Prometheus: Revert client test change from 1c503908
(cherry picked from commit 055c3b7332)
Co-authored-by: Fionera <fionera@fionera.de>
* Introduce a new feature flag for prometheus buffered client
* Use querydata client as default and put buffered client behind the feature flag
* Remove prometheusStreamingJSONParser feature flag as it is not needed anymore
* Update tests
* Fix unit tests
* Update feature flag description
* clean up and document integration test convention
* clarify integration test conventions
* clean up integration tests that don't follow convention
* mark testIntegration* functions as helpers to avoid confusion
Removes various custom headers logic sprinkled around in the backend.
It should automatically be applied to outgoing HTTP requests via the
CustomHeadersMiddleware.
This also removes decryption of SecureJSONData to populate custom
headers in ngalert which seemed to have caused a ton of CPU usage.
