[Feature] Enable openapi v3.1

[mtrimolet]

Upgrade dependencies (fastify, typescript, ..) and allow for schema using openapi v3.1 to be parsed

[mtrimolet]

Too many upgrades, I need to rebuild without non-core deps upgrades.

Is the support for node v8 still wanted though ? I see @types/node@12 being installed, and it prevents upgrading eslint, typescript, ...
I suppose we could upgrade CI to check from v10 (even v12 ?) through v17, and maybe specify engine versions requirement, matching the type used, in the package.json.

PS: even npm conflicts : package.lock is v2, so uses npm v7, which requires node >=10
(EDIT: extracting-out the openapi part seems ok, I just think we could also upgrade everything else)

[SomaticIT]

Is the support for node v8 still wanted though ? I see @types/node@12 being installed, and it prevents upgrading eslint, typescript, ...

Support for node v8 could be safely removed

I suppose we could upgrade CI to check from v10 (even v12 ?) through v17, and maybe specify engine versions requirement, matching the type used, in the package.json.

CI should be updated to test v10, v12, v14 and v16 (only LTS releases).

PS: even npm conflicts : package.lock is v2, so uses npm v7, which requires node >=10

The package-lock.json should be removed from the repo (and added to .gitignore) since it's not part of the published package. It will force contributors to have latest versions of dependencies instead of locked one (better match the npm i fastify-oapi behavior).

This also means we should replace npm ci by npm install in CI workflows

[mtrimolet]

I'll try the simple change here and make another PR for upgrading then

[mtrimolet]

Checks are obviously successful since I only changed some strings.
But maybe we should test an openapi v3.1 specific feature to ensure it's ok to accept it

[SomaticIT]

There are some breaking changes:
https://github.com/OAI/OpenAPI-Specification/releases

See: 3.1.0, 3.1.0-rc1, 3.1.0-rc0

The most notable one is the removal of nullable.

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We may also need to adjust ajv-openapi default options:

• allow to specify target OpenAPI version
• when 3.1: use draft-2020-12 jsonschema version
• when 3.1: set nullable to false
• when 3.1: do not include string format validator: byte

Maybe some others...