feat: Discovery service health check

[boris-bc]

Description

This change enables the discovery service health endpoint to return details even when not authenticated. Those details contain the status of the gateway service. The status of the gateway service does not influence the discovery service status, i.e. it remains UP even when the gateway is DOWN.

Sample status:

{"status":"UP","components":{"discoveryService":{"status":"UP","details":{"gateway":"DOWN"}}}}

Linked to #1549

Type of change

Please delete options that are not relevant.

• (feat) New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas. In JS I did provide JSDoc
• [n/a] I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The java tests in the area I was working on leverage @nested annotations
• [n/a] Any dependent changes have been merged and published in downstream modules

[CarsonCook]

This works and looks good to me, but a though, instead of having the overall status as UP, could we create a custom status like PARTIAL and the Status description is something like authenticated endpoints won't work? Just a thought, may not be valuable.

[boris-bc]

PARTIAL and the Status description is something like authenticated endpoints won't work

Yes, that sounds logical but there is a dependency in the gateway service on this status. The gateway wouldn't start unless the discovery service is up. By adding this new status to the discovery service, we would create a cyclical dependency.

[CarsonCook]

PARTIAL and the Status description is something like authenticated endpoints won't work

Yes, that sounds logical but there is a dependency in the gateway service on this status. The gateway wouldn't start unless the discovery service is up. By adding this new status to the discovery service, we would create a cyclical dependency.

We could change the logic to have the GW also start when PARTIAL is shown. Anyways, I think this is getting more complex than necessary, it was just a thought. Approved.

[boris-bc]

@CarsonCook , it turns out a PARTIAL status with HTTP code 200 does not require changes in the gateway service.
Please take a look at the latest commit. The new status looks similar to this:

{"status":"UP","components":{"discoveryService":{"description":"Authenticated endpoints not available.","status":"PARTIAL","details":{"gateway":{"status":"DOWN"}}}}}

[sonarqubecloud]

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