feat: add configuration_hash in /status in dbless

[shaneutt]

Summary

In #8152 it was reported that if the Kong Gateway crashes the KIC will not be aware and unless something changes in the control plane, it will not push a new configuration.

This patch adds a configuration_hash to the /status endpoint, which would help solve this problem (in DBLESS mode) by allowing the control-plane to keep track of changes to the hash on the data-plane and use that to make decisions about pushing new /config updates.

Issues resolved

Partially resolves Kong/kubernetes-ingress-controller#2107

[CLAassistant]

All committers have signed the CLA.

[shaneutt]

I tested this locally and it worked properly: I was able to verify that the hash and empty status message was populated only in dbless mode.

However there was some kind of issue with the #off strategy which I may need help with: it seemed as if the #off strategy did not turn on dbless mode because the /status output did not include the field when running the tests (but again, it did work when I did a manual test).

EDIT: well it ended up working in CI so perhaps it was a local environment issue?

[shaneutt]

Closing this in favor of #8256

[shaneutt]

@dndx suggested may still want this implementation for @Kong/team-k8s, re-opening.

[hbagdi]

+1 from an API perspective

[hbagdi]

The code should add a test to assert that the hash is populated correctly on the Admin API /status endpoint as well (the code tests for Status API /status).
KIC plans to use Admin API so if there is a regression here, it would be problematic for you, won't it?

[hbagdi]

This looks good from an API perspective.
Someone in team gateway who has more familiarity with this code can review this further and approve.

[RobSerafini]

@shaneutt @locao - It looks like this PR is ready to be merged. Any reason why it is not?

[locao]

Merged! Thanks for pointing out, @RobSerafini 👍