[BUG][typescript-fetch] HEAD missing in HTTPMethod for typescript-fetch client

Created by: yuannnh

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue? yes
• Have you validated the input using an OpenAPI validator (example)? yes
• What's the version of OpenAPI Generator used? 4.0.0
• Have you search for related issues/PRs? yes
• What's the actual output vs expected output? Expected output: Api run correctly. Actual output: TypeScript error: Type '"HEAD"' is not assignable to type 'HTTPMethod'
• [Optional] Bounty to sponsor the fix (example)

Description

While running generated API, I got TypeScript error: Type '"HEAD"' is not assignable to type 'HTTPMethod'

After checking the generated API's code, I found that there is HEAD value missing in type HTTPMechod.

runtime.ts

export type HTTPMethod =
  | "GET"
  | "POST"
  | "PUT"
  | "PATCH"
  | "DELETE"
  | "OPTIONS";

However in BasicErrorControllerApi.ts, we do use the HEAD method:

 async errorUsingHEADRaw(): Promise<
    runtime.ApiResponse<{ [key: string]: object }>
  > {
    const queryParameters: runtime.HTTPQuery = {};

    const headerParameters: runtime.HTTPHeaders = {};

    const response = await this.request({
      path: `/error`,
      method: "HEAD",
      headers: headerParameters,
      query: queryParameters
    });

    return new runtime.JSONApiResponse<any>(response);
  }

It works well after adding HEAD in HTTPMethod.

openapi-generator version

typescript-fetch 4.0.0

OpenAPI declaration file content or url