User creation in Joplin needs to behave better

As an admin within Joplin, I should be able to create a user without getting an error message.

Currently, if an admin creates a user and selects the "editor" or "moderator" role, which requires a department, it is not indicated in the interface. That means I get an error *after save*, and don't know what I've done wrong until I return to the "role" tab.

Department should dynamically show as required if the moderator/editor role is selected.[
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Start by locating the Joplin admin user-creation form and its role and department validation. Reproduce the error by selecting the editor or moderator role without a department, then trace the form behavior; done means the department is visibly required before saving and the misleading post-save error no longer occurs.

Written by the indexing model from the issue text.