codegen: limited support for oneOfVariant in responses

[hughsimpson]

Adding a bit of support for oneOfVariants. Where the previous code would've generated

.errorOut(jsonBody[MessageResponse].description("Bad Request").and(statusCode(sttp.model.StatusCode(400))))
.errorOut(jsonBody[MessageResponse].description("Forbidden").and(statusCode(sttp.model.StatusCode(403))))
.errorOut(jsonBody[MessageResponse].description("Not Found").and(statusCode(sttp.model.StatusCode(404))))
.errorOut(jsonBody[MessageResponse].description("Unauthorized").and(statusCode(sttp.model.StatusCode(401))))

we would now generate

.errorOut(oneOf(oneOfVariant(sttp.model.StatusCode(400), jsonBody[MessageResponse].description("Bad Request")), oneOfVariant(sttp.model.StatusCode(404), jsonBody[MessageResponse].description("Not Found")), oneOfVariant(sttp.model.StatusCode(403), jsonBody[MessageResponse].description("Forbidden")), oneOfVariant(sttp.model.StatusCode(401), jsonBody[MessageResponse].description("Unauthorized"))))

given

      responses:
        '400':
          description: Bad Request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessageResponse'
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessageResponse'
        '403':
          description: Forbidden
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessageResponse'
        '404':
          description: Not Found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessageResponse'

[hughsimpson]

Completely unrelated, but this can be triggered by surprising things (e.g. an object containing a property that's an enum without a type) so this helps avoid banging heads on walls or keyboards.

[adamw]

Thank you :)

[hughsimpson]

this could've been better I think

[adamw]

you mean 200?

[hughsimpson]

No, I mean, default should encompass other status codes; there's an implicit contract binding we take in our choice of code, but really this is explicitly an 'open' sort of specification.... I don't know how to express it well I'm afraid.