style(typescript): use Headers type (#19697)

modules/openapi-generator/src/main/resources/typescript/http/http.mustache

@@ -63,6 +63,8 @@ export class HttpException extends Error {
  */
 export type RequestBody = undefined | string | FormData | URLSearchParams;
 
+type Headers = Record<string, string>;
+
 function ensureAbsoluteUrl(url: string) {
     if (url.startsWith("http://") || url.startsWith("https://")) {
         return url;
@@ -81,7 +83,7 @@ function ensureAbsoluteUrl(url: string) {
  * Represents an HTTP request context
  */
 export class RequestContext {
-    private headers: { [key: string]: string } = {};
+    private headers: Headers = {};
     private body: RequestBody = undefined;
     private url: URL;
     {{#platforms}}
@@ -135,7 +137,7 @@ export class RequestContext {
         return this.httpMethod;
     }
 
-    public getHeaders(): { [key: string]: string } {
+    public getHeaders(): Headers {
         return this.headers;
     }
 
@@ -224,7 +226,7 @@ export class SelfDecodingBody implements ResponseBody {
 export class ResponseContext {
     public constructor(
         public httpStatusCode: number,
-        public headers: { [key: string]: string },
+        public headers: Headers,
         public body: ResponseBody
     ) {}
 
@@ -235,8 +237,8 @@ export class ResponseContext {
      * Parameter names are converted to lower case
      * The first parameter is returned with the key `""`
      */
-    public getParsedHeader(headerName: string): { [parameter: string]: string } {
-        const result: { [parameter: string]: string } = {};
+    public getParsedHeader(headerName: string): Headers {
+        const result: Headers = {};
         if (!this.headers[headerName]) {
             return result;
         }
@@ -316,7 +318,7 @@ export function wrapHttpLibrary(promiseHttpLibrary: PromiseHttpLibrary): HttpLib
 export class HttpInfo<T> extends ResponseContext {
     public constructor(
         public httpStatusCode: number,
-        public headers: { [key: string]: string },
+        public headers: Headers,
         public body: ResponseBody,
         public data: T,
     ) {