[Bug][typescript-fetch] Typescript fetch one of addtl props imports

[btpnlsl]

Closes #21587

The typescript-fetch client generator has a bug when generating model code where the list of imports will be missing items if the OAS spec includes a schema a oneOf section and the oneOf schema has additionalProperties: true.

An example OAS would be

openapi: 3.0.1
info:
  title: Example API
  version: 1.0.0
paths:
  /api/endpoint:
    get:
      operationId: GetEndpoint
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema:
                type: object
                title: OneOfResponse
                oneOf:
                  - $ref: '#/components/schemas/OptionOne'
                  - $ref: '#/components/schemas/OptionTwo'
components:
  schemas:
    OptionOne:
      type: object
      title: OptionOne
      properties:
        propOne:
          type: number
      additionalProperties: true
    OptionTwo:
      type: object
      title: OptionTwo
      properties:
        propTwo:
          type: string

The model code generated for OneOfResponse.ts includes the following type:
export type OneOfResponse = OptionOne | OptionTwo;

However, the imports in OneOfResponse.ts will only have imports for OptionTwo.

The underlying issue is that TypeScriptFetchClientCodegen.processCodeGenModel is creating a set of model imports by filtering out schemas using the CodegenProperty::getIsModel method.

        cm.oneOfModels = oneOfsList.stream()
                .filter(CodegenProperty::getIsModel)
                .map(CodegenProperty::getBaseType)
                .filter(Objects::nonNull)
                .collect(Collectors.toCollection(TreeSet::new));

Schemas which have additional properties set will not be marked as models because IJsonSchemaValidationProperties.setTypeProperties because ModelUtils.isModelWithPropertiesOnly evaluates to false due to the presence of the additional properties.

That probably wasn't the intention of the original PR #21057 (addressing #19909), which was to filter out imports for built-in language primitive types like string, object, Array, etc.

This PR changes the filter used in TypeScriptFetchClientCodegen to use .filter(cp -> !cp.getIsPrimitiveType() && !cp.isArrayType()) to filter out schemas for language built-in types or arrays.

The language built-in types are defined in AbstractTypeScriptClientCodegen as a combination between the -languageSpecificPrimitives variable and the default typeMapping. Types will be mapped first using the typeMapping map and then be compared against the list of language specific primitives.

I've added a unit test for this bug using the OAS issue_21587.yaml which uses a oneOf composed of a schema with additionalProperties: true and also a bunch of primitive types which should hit most of primitives available with the default type mappings.

One area I wasn't entirely 100% on is the use of Set as a primitive. My understanding is that the Set type is only available starting with ES6. The typescript client generators have a setting, supportsES6, which is false by default. I'm not sure how valid it is to have Set as a language primitive type if supportsES6 is false.

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Typescript: @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04) @joscha (2024/10)
Prior work: PR #21057 - @GregoryMerlet

[macjohnny]

thanks for the fix!