Implement /oauth2/token endpoint; token auth middleware

src/http/lifecycle/Response.ts

@@ -109,6 +109,20 @@ export class Response {
         return this
     }
 
+    /**
+     * Remove a header from the response by name.
+     * @param name
+     */
+    public unsetHeader(name: string): this {
+        this.logging.verbose(`Will unset header on response: ${name}`)
+        if ( this.sentHeaders ) {
+            throw new HeadersAlreadySentError(this, name)
+        }
+
+        delete this.headers[name]
+        return this
+    }
+
     /**
      * Bulk set the specified headers in the response.
      * @param data