feat(health): add option to enable/disable openapi spec

[nflaig]

Adds the option to enable the openapi spec which allows to show the endpoints in the API explorer. By default it will be disabled.

Checklist

• DCO (Developer Certificate of Origin) signed in all commits
• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated

[nflaig]

@raymondfeng should the HealthChecker and HealthObserver be added to the application if the options.disabled is true?

Also one more thing, does it make sense to add 500 and 503 to the responses in the spec or is just the 200 response enough?

[raymondfeng]

@nflaig Please note that CI is failing - https://github.com/strongloop/loopback-next/pull/6645/checks?check_run_id=1311555675

[raymondfeng]

should the HealthChecker and HealthObserver be added to the application if the options.disabled is true?

Interesting, if we decide to disable health component, we can simply remove app.component(HealthComponent). So far the behavior of disabled: true is to not expose the http endpoints. I think we can leave it out of this PR.

[nflaig]

Interesting, if we decide to disable health component, we can simply remove app.component(HealthComponent).

I agree that one could just put a if-statement around the app.component(HealthComponent) to disable it through the config, however it does feel like the cleanest approach to me. But I guess this also depends on how the configuration in the app that is using the component is handled in general.

I think we can leave it out of this PR

agreed

[raymondfeng]

@nflaig One more PR landed. Great job! 🥇