How can I proxy multiple LDAP servers with completely different name spaces?

We are developing R/Shiny Applications on Ubuntu Server. Authentication is done via OpenLDAP on Ubuntu Server. The Shiny Server only supports one LDAP directory. Now, we have an external customer which would like to connect to our applications with their own LDAP.

So, we have the following setup right now:

OpenLDAP (dc="ourcompany", dc="com") --> R/Shiny Application.

The customer's ldap has a completely different namespace (dc="customercompany", dc="net").

I noticed the meta backend (https://linux.die.net/man/5/slapd-meta) but can't find our scenario. All I can find is scenarios for multiple LDAP servers which share certain parts of the namespace.

There is also a similar question here (How can I proxy multiple LDAP servers, and still have grouping of users on the proxy?) but it seems also for two servers which share parts of the namespace.

Am I missing something?

Is there any way I can proxy the two LDAP directories (dc="ourcompany", dc="com"); (dc="customercompany", dc="net") to one LDAP direcory e.g. (dc="ourcompany-customercompany", dc="com")?

Thanks for any help you can provide.