Add authenticationMethod to the authentication response serializer (#1031)

## 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.

Author: hadihallak

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

@@ -1,12 +1,21 @@
 import { Impersonator, ImpersonatorResponse } from './impersonator.interface';
 import { User, UserResponse } from './user.interface';
 
+type AuthenticationMethod =
+  | 'SSO'
+  | 'Password'
+  | 'GitHubOAuth'
+  | 'GoogleOAuth'
+  | 'MicrosoftOAuth'
+  | 'MagicAuth'
+  | 'Impersonation';
 export interface AuthenticationResponse {
   user: User;
   organizationId?: string;
   accessToken: string;
   refreshToken: string;
   impersonator?: Impersonator;
+  authenticationMethod?: AuthenticationMethod;
 }
 
 export interface AuthenticationResponseResponse {
@@ -15,6 +24,7 @@ export interface AuthenticationResponseResponse {
   access_token: string;
   refresh_token: string;
   impersonator?: ImpersonatorResponse;
+  authentication_method?: AuthenticationMethod;
 }
 
 export interface RefreshAuthenticationResponse {

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

@@ -14,6 +14,7 @@ export const deserializeAuthenticationResponse = (
     organization_id,
     access_token,
     refresh_token,
+    authentication_method,
     impersonator,
     ...rest
   } = authenticationResponse;
@@ -24,6 +25,7 @@ export const deserializeAuthenticationResponse = (
     accessToken: access_token,
     refreshToken: refresh_token,
     impersonator,
+    authenticationMethod: authentication_method,
     ...rest,
   };
 };

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

@@ -163,6 +163,25 @@ describe('UserManagement', () => {
       });
     });
 
+    it('deserializes authentication_method', async () => {
+      fetchOnce({
+        user: userFixture,
+        authentication_method: 'Password',
+      });
+
+      const resp = await workos.userManagement.authenticateWithCode({
+        clientId: 'proj_whatever',
+        code: 'or this',
+      });
+
+      expect(resp).toMatchObject({
+        user: {
+          email: '[email protected]',
+        },
+        authenticationMethod: 'Password',
+      });
+    });
+
     describe('when the code is for an impersonator', () => {
       it('deserializes the impersonator metadata', async () => {
         fetchOnce({