Upgrade openapi to 3.1

[snebjorn]

Major refactor changes

OpenAPI parsers, validators, loaders, upgraders, etc have all been switched to https://github.com/scalar/scalar
Input specs are upgraded to OpenAPI 3.1 and all functions get served OpenAPI 3.1 so no longer a mix of 3.0 and 3.1

All specs and schemas are no longer passed to functions along a spec key so they needed to pick the correct schema. Instead only the relevant spec and schema is passed to functions. Hopefully this makes things easier.
Example:

// before
specs.reduce(unreadable code...
context.specs[specKey]
// now
spec
context.spec

Note

SchemaObject is union-typed with a boolean, this is because the OpenAPI spec allows for this

The empty schema (which allows any instance to validate) MAY be represented by the boolean value true and a schema which allows no instance to validate MAY be represented by the boolean value false.
https://swagger.io/specification/

However this screws up the type. So in order to fix this a type-guard excluding the boolean must be used, and also handle the boolean case. Pretty annoying - but that's in spec.

A lot of types can be either "the thing" or a reference to a thing. We have isReference (and still do) but now we also have { isDereferenced } from '@scalar/openapi-types/helpers' which is the reverse, but gives better types then !isReference

Nullable types are now harder to "detected" thanks to OpenAPI 3.1

# OpenAPI v3.0
type: string
nullable: true

# OpenAPI v3.1
type:
- "string"
- "null" 

https://www.openapis.org/blog/2021/02/16/migrating-from-openapi-3-0-to-3-1-0

We need to do something better then what I did, because null is now in the type prop and it's an array and... and...
const isNullable = isArray(schema.type) && schema.type.includes('null')

Caution

BREAKING CHANGES

• input.validation is gone. input spec is now always validated, as well as transformer output.
• input.parserOptions is gone. New parser doesn't take swagger options.
• input.converterOptions is gone.
• InputFiltersOption renamed InputFiltersOptions
• generated filenames and models may change name from prior versions

Plus I expect some regressions

FEATURES

• cli argument --project now accepts a list of projects. Example: --project dogstore catstore

[melloware]

Nice looks like all tests are passing!

[snebjorn]

Yep, hopefully this doesn't break stuff I'm not aware of :)

[melloware]

Well we will find out I will do another RC release so we can test.