feat(health-indicator): add mikro-orm health indicator

[jbw]

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
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PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the new behavior?

Adds mikro-orm health indicator

Issue Number: #1877

Does this PR introduce a breaking change?

• Yes
• No

Other information

[BrunnerLivio]

LGTM so far. I'll check it out locally asap :) Thanks a lot, really appreicated!

[jbw]

LGTM so far. I'll check it out locally asap :) Thanks a lot, really appreicated!

The unit tests failed here but not sure why. Does work locally though 😉

[micalevisk]

@jbw they failed in node10 because the operator ?? was introduced in node14. Not sure how we could fix that as that code isn't in our side 🤔

[jbw]

@jbw they failed in node10 because the operator ?? was introduced in node14. Not sure how we could fix that as that code isn't in our side 🤔

Downgrading Mikro that far back to v2 or v3 won't work either as the library is not compatible with newer versions. v4 onwards supports Node 14+

@BrunnerLivio @micalevisk I noticed the e2e tests support only v14. I wonder if it is safe to drop v10 and v12 from the unit tests?

[micalevisk]

Kamil still want to support node 10. So I guess isn't that safe to remove those unit tests in @nestjs/* packages.

Maybe we can drop the support for node10 only for the mikro-orm part somehow. And then we should verify that in the action so we could skip it

[BrunnerLivio]

I'm doing some further experiments on this. Theoretically, it should be possible to keep Node v10 support with Terminus - unless you use MikroOrm off course - since we optionally load third-party dependencies. I'll close this PR and continue it over at #1879. Off course, contributions are welcome there as well.

FYI:

• If I am not mistaken I was able to run NestJS Terminus with Node v10 + the changes from this PR. I published @nestjs/terminus@beta with the changes from this PR to test it. Need to dig a bit deeper but so far it seems feasible.

• I am currently struggling with getting the MikroORM provider without importing the MikroORM class itself. Terminus does this so in the type definition file there are no references to MikroORM so TypeScript does not complain in case the dependency is not installed.

I am trying it this way currently, no luck so far.

terminus/lib/health-indicator/database/mikro-orm.health.ts

Lines 105 to 106 in a2a50a1

	const { MikroORM } = require('@mikro-orm/nestjs') as typeof MikroOrmNestJS;
	const mikro = this.moduleRef.get(MikroORM, { strict: false });

Will need to dig deeper in the following days