typescript-axios string date format

Created by: tsiq-jeremy

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Description of the PR

@TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny

Fair warning that I tested this out more thoroughly using swagger-codegen for this PR - https://github.com/swagger-api/swagger-codegen/pull/9594 - but it looks like the same exact issue.

Related to this issue. When using TypeScript Fetch and passing parameters to a "Date" field, they expect a type of "string", but then toISOString() is called on it, which causes the function to fail.

Example json swagger:

        "parameters": [
          {
            "name": "date",
            "in": "query",
            "type": "string",
            "format": "date"
          }
        ]

in In `AbstractTypeScriptClientCodegen.java the Typings map:

typeMapping.put("date", "string");
typeMapping.put("DateTime", "Date");

template issue:

{{#isDate}}
queryParameters['{{baseName}}'] = (requestParameters.{{paramName}} as any).toISOString();
{{/isDate}}

requestParameters.{{paramName}} can never be a Date, since it has to be a string.

fixes https://github.com/OpenAPITools/openapi-generator/issues/2745