Add support for named enums

[Colmea]

Hi all,

I don't want to create an issue since this feature is not officially supported in the OpenAPI spec, but I think we can trigger a discussion on this topic:
How to support named enums ?

Currently, none of the 2 solutions proposed below generate a proper typescript enum.

Few solutions has been proposed:

Support custom x- property

Adding a custom "x-..."property in the OpenAPI schema.

• NSwag support "x-enumNames"
• AutoRest support "x-ms-enum"

Example:

"SortDirection": {
  "type": "integer",
  "x-enumNames": ["Asc", "Desc"],
  "enum": [0, 1]
},

Few typescript codegen tool support this:

• openapi-typescript-codegen support the "x-enum-varnames" property
• openapi-typescript support the "x-enumNames" from NSwag

Use "oneOf" from OpenAPI 3.1

This is the official OpenAPI response on this.
use oneOf combined with "title" and "const":

Severity:
  type: integer
  oneOf:
  - title: HIGH
    const: 2
    description: An urgent problem
  - title: MEDIUM
    const: 1
  - title: LOW
    const: 0
    description: Can wait forever

I'm not a big fan on this because it's not supported by OpenAPI codegen tools.

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Do you have any input on this @astahmer ?

Btw, I would be happy to propose a PR to support the first solution