To be honest, if you have to ask it's probably not one you're having. Things like this tend to be quite application specific. Generally, if you're doing much with AD directly, you'd be doing it via LDAP. However, if you need to talk to it (for some reason) through a web application -- this just might be helpful.

The problem of not having an Active Directory REST API.

I have a bunch of engineers that can presumably automate the provisioning and de-provisioning of the LDAP user accounts without having to mess around with the AD. I hire a consultant (think MSP) to set up and maintain the LDAP hosts and have my engineers write the necessary scripts to perform the aforementioned. This is beneficial for security automation, especially, in the cases where a company is too small to afford a dedicated IT SMEs but large enough to be able to afford something like SSAE-18 SOC 2 Type 2 (or equivalent). In those cases, the security automation in itself presents a repeatable process, which can be verified given the scripts would be executed using a job (Jenkins). This project fits that mold perfectly because that I have dealt with the exact scenario nth times with many start-ups operating in the B2B world with security stipulations such as ISO 27xxx or SOC 2 Type 2.

There are other ways to do it, but if you wanted, for example, to build a tool for employee on-boarding/off-boarding as web app, this might be helpful. Or maybe adding password change to an existing web app that authenticates via AD.

There are existing REST apis for AD, so I don't know what this brings that's new.