### 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_
return None
# TODO maybe move to a different place?
# Basic Transformation - added automatically to each snapshot (in the fixture)
SNAPSHOT_BASIC_TRANSFORMER = [
    ResponseMetaDataTransformer(),
    KeyValueBasedTransformer(
        lambda k, v: (
            v
            if (isinstance(v, str) and k.lower().endswith("id") and re.match(PATTERN_UUID, v))
            else None
        ),
        "uuid",
    ),
    RegexTransformer(PATTERN_ISO8601, "date"),
    KeyValueBasedTransformer(
        lambda k, v: (v if isinstance(v, datetime) else None), "datetime", replace_reference=False
    ),
    KeyValueBasedTransformer(
        lambda k, v: str(v)
        if (
            re.compile(r"^.*timestamp.*$", flags=re.IGNORECASE).match(k)
            or k in ("creationTime", "ingestionTime")
        )
        and not PATTERN_ISO8601.match(str(v))
        else None,
        "timestamp",
        replace_reference=False,
    ),
]