Create a membership
Ensures an active membership for the given email will be provisioned.
- If the user already exists, they will be added to the requestor's organization.
- If it doesn't exist, a new user will be provisioned.
`role_id` can be one of `'admin'`, `'superuser'`, `'user'` or `'restricteduser'` for the corresponding predefined role, or an ID of a [Role](https://developer.close.com/api/resources/roles).
This request requires "Manage Organization" permissions.
API access to this endpoint is supported via OAuth only.