After studying https://pimcore.com/docs/5.x/Development_Documentation/Web_Services/index.html I am wondering if it's possible to create new users by creating new objects? This by passing on username and password, and let Pimcore hash the password itself.
Asking this because we probably want to implement business logic on another server and just use Pimcore's API for now.
I don't think it is possible to do it by the webservice of Pimcore, that's is based only on classes that are defined.
You can create a API by your own and extend the AbstractRestController and write a function there that creates user accounts.
Transferring user accounts with raw passwords doesn't sound to me as a solid architectural way to handle user logins over different systems, would recommend to implement a SAML provider that handles the logins of the application.