Include policy in warrant deserialization (#1125)

## Description

- Updates `Warrant` deserializer to include policy from
`WarrantResponse`

## 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/fga/fga-live-test.spec.ts

@@ -671,6 +671,7 @@ describe.skip('FGA Live Test', () => {
       resource: newPermission,
       relation: 'member',
       subject: user2,
+      policy: 'region == "us"',
     });
     expect(warrant2.warrantToken).toBeDefined();
 
@@ -684,6 +685,7 @@ describe.skip('FGA Live Test', () => {
     expect(warrants1.data[0].relation).toEqual('member');
     expect(warrants1.data[0].subject.resourceType).toEqual('user');
     expect(warrants1.data[0].subject.resourceId).toEqual(user2.resourceId);
+    expect(warrants1.data[0].policy).toEqual('region == "us"');
 
     const warrants2 = await workos.fga.listWarrants(
       { limit: 1, after: warrants1.listMetadata.after },

src/fga/fga.spec.ts

@@ -506,6 +506,7 @@ describe('FGA', () => {
               resource_type: 'user',
               resource_id: 'user_124',
             },
+            policy: 'region == "us"',
           },
         ],
         list_metadata: {
@@ -533,6 +534,7 @@ describe('FGA', () => {
             resourceType: 'user',
             resourceId: 'user_124',
           },
+          policy: 'region == "us"',
         },
       ]);
     });

src/fga/interfaces/warrant.interface.ts

@@ -72,4 +72,5 @@ export interface WarrantResponse {
   resource_id: string;
   relation: string;
   subject: SerializedSubject;
+  policy?: string;
 }

src/fga/serializers/warrant.serializer.ts

@@ -9,4 +9,5 @@ export const deserializeWarrant = (warrant: WarrantResponse): Warrant => ({
     resourceId: warrant.subject.resource_id,
     relation: warrant.subject.relation,
   },
+  policy: warrant.policy,
 });