SDK: assigning a role to a policy when creating or updating it, always fails

### Describe the Bug

I'm creating a series of scripts to set up multi-tenancy programmatically.

I'm using the SDK v19.1.0.

**ISSUE**
Assigning a role when creating/updating a policy always makes the call fail despite the policy object having a roles property (so I'm assuming it's doable)
https://docs.directus.io/reference/system/policies.html

Similarly, assigning a policy to a role makes it fail despite the role object having a policies property
https://docs.directus.io/reference/system/roles.html

So it seems like the problem is related to creating the necessary relationship in the directus_access table.

Functions I tested that present the same problem:
- createPolicy
- createPolicies
- updatePolicy
- updateRole

### To Reproduce

Test script to replicate the issue when creating a policy assigned to a specific role:

```
require('dotenv').config();

const DIRECTUS_URL = process.env.DIRECTUS_URL;
const DIRECTUS_ADMIN_EMAIL = process.env.DIRECTUS_ADMIN_EMAIL;
const DIRECTUS_ADMIN_PASSWORD = process.env.DIRECTUS_ADMIN_PASSWORD;

const userRole = {
id: 'replace-with-existing-role-id',
name: 'User'
};

const {
createDirectus,
rest,
login,
staticToken,
createPolicy,
} = require('@directus/sdk'); // "@directus/sdk": "^19.1.0"

async function setupPolicies() {
try {
console.log('Starting policies setup...');

// Get the token using a temporary client
console.log('Authenticating with Directus...');
const tempClient = createDirectus(DIRECTUS_URL)
.with(rest());

let loginResult;

try {
loginResult = await tempClient.request(
login(DIRECTUS_ADMIN_EMAIL, DIRECTUS_ADMIN_PASSWORD)
);
console.log('Successfully authenticated with Directus');
} catch (error) {
console.error('Failed to authenticate with Directus:', error);
throw error;
}

// Create a new client with the static token
const directus = createDirectus(DIRECTUS_URL)
.with(staticToken(loginResult.access_token))
.with(rest());

console.log('Setting up policy for User role...');

try {
const policyName = 'Read Own User Profile';
const policyDescription = 'Allows users to read their own user profile';

console.log(`Creating new policy "${policyName}" for role ${userRole.name} (${userRole.id})`);
const policy = await directus.request(createPolicy({
name: policyName,
description: policyDescription,
admin_access: false,
app_access: false,
roles: [userRole.id],
}));

console.log(`Successfully created policy with ID: ${policy.id}`);

} catch (error) {
console.error('Failed to set up User role policies:', error);
throw error;
}

} catch (error) {
console.error('Fatal error during policies setup:', error);
throw error;
}
}

// Run the setup
setupPolicies()
.then(() => console.log('Setup completed successfully'))
.catch(error => {
console.error('Setup failed:', error);
process.exit(1);
});
```

### Directus Version

v11.6.1

### Hosting Strategy

Self-Hosted (Docker Image)

### Database

PostgreSQL 17.4