Great seeing you again!
I would say that your use-case would be very well suited for our Auth0 Organizations feature which can allow a user to have a single identity ( based on their unique user_id ) while also being part of multiple dealerships ( Organizations ) with separate roles for each of them. You can then assign specific users to each Organization, specific applications and databases and brand them individually.
The major obstacle with this implementation is the restriction on the number of Organizations that can be created per tenant, in accordance with the subscription level ( more information can be found on our Pricing page ). While a free tenant supports 5 Organizations, having a large number ( more than 10/tenant) would require an Enterprise Subscription.
In case a multi-tenancy architecture is possible instead of one Enterprise tenant, you will need to create the user in multiple tenants, which I believe is not the best user experience having them access separate tenants. This being said, if you create the user via the Management API, you are able to specify the user_id when creating the user, which can result in having one user, with the same user_id, across multiple tenants. Otherwise, it it not possible to change the user_id value for existing users or create multiple users with the same id, more documentations for reference :
- Changing user_id values for custom database users
- Change user_id value of User in User managemet
- Modify the User ID Format
To fulfil the role part of your request, this can be accomplished via our Role-Based Access Control feature, that allows the assignment of specific roles to users in order to granulate their access and control level. This can be applied on an Organization level and Add Roles to Organization Members that allows you control over what a user can manage on that level as well and also grant different roles for each Organization that the user is a part of. If they need to have, for example, an Admin role in one Org and a Helpdesk role in another, this is possible and is detailed in the above-mentioned documentation.
Your use-case can present high architectural challenges and I do recommend getting in touch with out Support team to further establish a road map for this implementation.
Hope this helped!
Gerald