[BUG] [angular-typescript] Incorrect JSON object in HTTP request multipart form data

[Beaurpi]

Hi there,

I've figured out that there is an issue with the code generated, when using a multipart/form-data object.
Declare a POST method with the following requestBody:

'/test/upload':
post:
requestBody:
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                name:
                  type: string
                title:
                  type: object
                  properties:
                    en:
                      type: string
                    fr:
                      type: string
                fileName:
                  type: string
                  format: binary

It's related to the generated code in angular typescript.
in the generation command line i'm using the following:
-g typescript-angular

the generated service will have a good signature:
public uploadFile(id: string, name?: string, title?: UploadTitle, .....

But the HTTP post, will not pass a JSON for the parameter 'TITLE'.
It will actually encode the object as string.
As a result the 'title' parameter will be

-----------------------------8302951520691
Content-Disposition: form-data; name="title"

[object: Object]

Instead the parameter title should be

-----------------------------8302951520691
Content-Disposition: form-data; name="title"

{ en: 'sometext', fr: 'loren ipsum' }

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[macjohnny]

I guess the problem is due to the following lines of code:

openapi-generator/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache

Lines 316 to 317 in 044961f

	return this.httpClient.{{httpMethod}}{{^isResponseFile}}<{{#returnType}}{{{returnType}}}{{#isResponseTypeFile}}|undefined{{/isResponseTypeFile}}{{/returnType}}{{^returnType}}any{{/returnType}}>{{/isResponseFile}}(`${this.configuration.basePath}{{{path}}}`,{{#isBodyAllowed}}
	{{#bodyParam}}{{paramName}}{{/bodyParam}}{{^bodyParam}}{{#hasFormParams}}convertFormParamsToString ? formParams.toString() : formParams{{/hasFormParams}}{{^hasFormParams}}null{{/hasFormParams}}{{/bodyParam}},{{/isBodyAllowed}}

openapi-generator/modules/openapi-generator/src/main/resources/typescript-angular/api.service.mustache

Line 287 in 044961f

convertFormParamsToString = true;

@Beaurpi would you like to give it a try and implement a fix?

[Beaurpi]

@macjohnny That would be a pleasure. I would be totally newbie in .moustache things and this project.
So I think it would be better that someone else is taking care of this. I am missing a bit of time to get deep inside the project though...