chore: move mongodb to devDeps and add it to peerDeps

[rtritto]

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[gurgunday]

Thanks for the PR!

If I understand peerDeps correctly, this risks not installing mongoDB if a user installs packages using npm ci --omit=dev

[rtritto]

The default value of omit option is dev.
From npm version >= 7 (Node version >= 16) peer dependencies are autoinstalled: source.
Imply that mongodb, as peer dependency, will be installed with omit=dev.

[mcollina]

Unfortunately the minimum supported version of this module is Node v14.

[mcollina]

Generically we prefer to stay away from peerdependencies because they create more problems than what they are worth.

[rtritto]

Unfortunately the minimum supported version of this module is Node v14.

For mongodb v6 the minimum supported Node.js version is v16.20.1 (source).

[gurgunday]

Oof, that's correct, good catch

A PR that downgrades it is welcome

[mcollina]

I would really prefer avoiding peerDependencies anyway. They are just a source of headaches for maintainers.

[rtritto]

Node v14 isn't mantained, when it will be removed?

[gurgunday]

When Fastify v5 is released (probably by the end of this year)

[climba03003]

I am closing the PR because we avoid using peerDependencies in any case.
So, it is not going to merge in anytime.