@plusone-nick
I didn't check the part of our code that manage user creation for ages, but 99% sure, that you don't need to provide a password, or not even a username just an email.
Then you create the invite link with a second request if you want to have the onboarding process managed by cloudron.
Personal note:
Remember that as the server owner you are responsible for the content hosted in it, for this is normally a good idea to have some manual approval before creating an account from a form; or you have to provide a good moderation.