Update storage policy assignment

curl -X PUT https://api.box.com/2.0/storage_policy_assignments/932483 \
     -H 'Authorization: Bearer <ACCESS_TOKEN>'
     -H 'Content-Type: application/json" '
     -d '{
       "storage_policy": {
         "type": "storage_policy",
         "id": "1434325"
       }
     }'

// Reassign user 1234 to storage policy 7
BoxStoragePolicyAssignment assignment = await client.StoragePoliciesManager
    .UpdateStoragePolicyAssignment(assignmentId: "dXNlcl8yMjIyMg==", policyId: "7");

BoxStoragePolicyAssignment storagePolicyAssignment = new BoxStoragePolicyAssignment(api, "ASSIGNMENT_ID");
BoxStoragePolicyAssignment.Info assignmentInfo = storagePolicyAssignment.new Info();
assignmentInfo.setStoragePolicyID("NEW_STORAGE_POLICY_ID");
storagePolicyAssignment.updateInfo(assignmentInfo);

updated_storage_policy = {'storage_policy': {'type': 'storage_policy', 'id': '12345'}}
updated_assignment = client.storage_policy_assignment(assignment_id='ZW50ZXJwcmldfgeV82MDMwMDQ=').update_info(updated_storage_policy)
print('Update storage policy ID is {0}'.format(updated_assignment.storage_policy.id))

// Reassign user 22222 to storage policy 10
var assignmentID = 'dXNlcl8yMjIyMg==';
var updates = {
    storage_policy: {
        type: 'storage_policy',
        id: '10'
    }
};

client.storagePolicies.updateAssignment(assignmentID, updates)
    .then(updatedAssignment => {
        /* updatedAssignment -> {
            type: 'storage_policy_assignment',
            id: 'dXNlcl8yMjIyMg==',
            storage_policy: 'storage_policy', id: '10' },
            assigned_to: { type: 'user', id: '22222' } }
        */
    });

client.storagePolicy.updateAssignment(storagePolicyAssignmentId: "1234", storagePolicyId: "123") { (result: Result<StoragePolicyAssignment, BoxSDKError>) in
    guard case let .success(assignment) = result else {
        print("Error updating a storage policy assignment")
        return
    }
    print("Updated storage policy assignment \(assignment.id)")
}