feat: Add subuser impersonation to client (#600)

Sendgrid API has an (as yet) undocumented feature allowing parent accounts to impersonate
subusers by including an HTTP header "On-Behalf-Of" in each API request.
This commit enables setting the value for impersonation when creating the
Sendgrid API Client instance.

Author: CaptainYarb

packages/client/src/classes/client.js

@@ -18,6 +18,7 @@ const TWILIO_BASE_URL = 'https://email.twilio.com/';
 class Client {
   constructor() {
     this.auth = '';
+    this.impersonateSubuser = '';
 
     this.defaultHeaders = {
       Accept: 'application/json',
@@ -65,6 +66,10 @@ class Client {
     return typeof value === 'string' || value instanceof String;
   }
 
+  setImpersonateSubuser(subuser) {
+    this.impersonateSubuser = subuser;
+  }
+
   setDefaultHeader(key, value) {
     this.defaultHeaders[key] = value;
     return this;
@@ -84,6 +89,10 @@ class Client {
       headers.Authorization = this.auth;
     }
 
+    if (this.impersonateSubuser) {
+      headers['On-Behalf-Of'] = this.impersonateSubuser;
+    }
+
     return headers;
   }
 

packages/client/src/client.d.ts

@@ -15,6 +15,11 @@ declare class Client {
    */
   setTwilioEmailAuth(username: string, password: string): void;
 
+  /**
+   * Set client requests to impersonate a subuser
+   */
+  setImpersonateSubuser(subuser: string): void;
+
   /**
    * Set default header
    */

packages/client/src/client.spec.js

@@ -76,6 +76,16 @@ describe('client', () => {
   });
 });
 
+describe('setImpersonateSubuser', () => {
+  const impersonateSubuser = 'abcxyz@this.is.a.test.subuser';
+  const sgClient = require('./client');
+  sgClient.setImpersonateSubuser(impersonateSubuser);
+
+  it('should set the imperonate subuser header', () => {
+    expect(sgClient.impersonateSubuser).to.equal(impersonateSubuser);
+  });
+});
+
 describe('test_access_settings_activity_get', () => {
   const request = {};
   request.qs = {