Share users between two instances of gitlab


I wonder if it is possible to share the registered users of one gitlab instance with another one.
Here is the “why” :
We have a development-dedicated gitlab. This is about C++, scripts, etc. For regulatory reasons, we want to manage our documentation through gitlab (as it is written in latex). This is at corporation level, so it has to be a strict separation between both gitlab (ideally on 2 different VMs)
However, I know people are lazy (me first) and it would be tedious to have 2 logins, one for each gitlab.

Thanks for your tips!