### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to list roles where permission boundaries are attached the response cannot be serialized 

`aws --endpoint-url=http://localhost:4566 iam list-roles --region ap-southeast-2`
```
An error occurred (InternalError) when calling the ListRoles operation (reached max retries: 2): exception while calling iam.ListRoles: Invalid type when serializing AttachedPermissionsBoundary: '<Element 'member' at 0xffff8275ef20>' cannot be parsed to structure.
```

### Expected Behavior

Expect that all roles are listed

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

* Create an IAM policy
* Create an IAM role which used the policy as a permission boundary
* Attempt to list all roles with `aws --endpoint-url=http://localhost:4566 iam list-roles --region ap-southeast-2`


### Environment

```markdown
- OS: MacOS
- LocalStack: latest
```


### Anything else?

_No response_
aws_client.iam.untag_instance_profile(InstanceProfileName=user_name, TagKeys=tags_u_v1)
        #
        rs = aws_client.iam.list_instance_profile_tags(InstanceProfileName=user_name)
        assert rs["Tags"] == target_tags_u_v1
        tags_u_v2 = [f"key-{long_uid()}"]
        target_tags_u_v2 = target_tags_u_v1
        aws_client.iam.untag_instance_profile(InstanceProfileName=user_name, TagKeys=tags_u_v2)
        #
        rs = aws_client.iam.list_instance_profile_tags(InstanceProfileName=user_name)
        assert rs["Tags"] == target_tags_u_v2
        tags_u_v3 = [tag["Key"] for tag in target_tags_u_v1]
        target_tags_u_v3 = []
        aws_client.iam.untag_instance_profile(InstanceProfileName=user_name, TagKeys=tags_u_v3)
        #
        rs = aws_client.iam.list_instance_profile_tags(InstanceProfileName=user_name)
        assert rs["Tags"] == target_tags_u_v3
        aws_client.iam.delete_instance_profile(InstanceProfileName=user_name)
    def test_create_user_with_tags(self, aws_client):
        user_name = "user-role-{}".format(short_uid())
        rs = aws_client.iam.create_user(
            UserName=user_name, Tags=[{"Key": "env", "Value": "production"}]
        )
        assert "Tags" in rs["User"]
        assert rs["User"]["Tags"][0]["Key"] == "env"
        rs = aws_client.iam.get_user(UserName=user_name)
        assert "Tags" in rs["User"]
        assert rs["User"]["Tags"][0]["Value"] == "production"
        
        aws_client.iam.delete_user(UserName=user_name)
    def test_attach_detach_role_policy(self, aws_client):