Add multiple roles support (#1358)

## Description

- Add `roles` to organization membership resource responses (get, list,
create, update, deactivate, reactivate)
- Add `roleSlugs` parameter to organization membership create and update
options
- Add `roles` support to session authentication and JWT decoding

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[X] Yes
```

Will update the docs for these changes in **ENT-3687**

## Testing

Tested locally against a team with multiple roles enabled. I tested OM
get and update, along with the user management auth flow.