Add profile_picture_url attribute to the user object (#958)

## Description

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[ ] Yes
```

If yes, link a related docs PR and add a docs maintainer as a reviewer.
Their approval is required.

src/user-management/fixtures/user.json

@@ -6,5 +6,6 @@
   "last_name": "User",
   "created_at": "2023-07-18T02:07:19.911Z",
   "updated_at": "2023-07-18T02:07:19.911Z",
-  "email_verified": true
+  "email_verified": true,
+  "profile_picture_url": "https://example.com/profile_picture.jpg"
 }

src/user-management/interfaces/user.interface.ts

@@ -3,6 +3,7 @@ export interface User {
   id: string;
   email: string;
   emailVerified: boolean;
+  profilePictureUrl: string | null;
   firstName: string | null;
   lastName: string | null;
   createdAt: string;
@@ -14,6 +15,7 @@ export interface UserResponse {
   id: string;
   email: string;
   email_verified: boolean;
+  profile_picture_url: string | null;
   first_name: string | null;
   last_name: string | null;
   created_at: string;

src/user-management/serializers/user.serializer.ts

@@ -6,6 +6,7 @@ export const deserializeUser = (user: UserResponse): User => ({
   email: user.email,
   emailVerified: user.email_verified,
   firstName: user.first_name,
+  profilePictureUrl: user.profile_picture_url,
   lastName: user.last_name,
   createdAt: user.created_at,
   updatedAt: user.updated_at,

src/user-management/user-management.spec.ts

@@ -29,6 +29,7 @@ describe('UserManagement', () => {
         object: 'user',
         id: 'user_01H5JQDV7R7ATEYZDEG0W5PRYS',
         email: 'test01@example.com',
+        profilePictureUrl: 'https://example.com/profile_picture.jpg',
         firstName: 'Test 01',
         lastName: 'User',
         emailVerified: true,
@@ -93,6 +94,7 @@ describe('UserManagement', () => {
         firstName: 'Test 01',
         lastName: 'User',
         emailVerified: true,
+        profilePictureUrl: 'https://example.com/profile_picture.jpg',
         createdAt: '2023-07-18T02:07:19.911Z',
         updatedAt: '2023-07-18T02:07:19.911Z',
       });
@@ -380,6 +382,7 @@ describe('UserManagement', () => {
       });
       expect(resp).toMatchObject({
         email: 'test01@example.com',
+        profilePictureUrl: 'https://example.com/profile_picture.jpg',
       });
     });
 
@@ -399,6 +402,7 @@ describe('UserManagement', () => {
         });
         expect(resp).toMatchObject({
           email: 'test01@example.com',
+          profilePictureUrl: 'https://example.com/profile_picture.jpg',
         });
       });
     });