* fix: actualy remove special characterso
`or "_"` is always truthy, this code didn't do anything
* refactor!: Prefix all custom fieldnames created from Desk
Why?
- Custom and standard field clashes are frequent. This will prevent it
from happening. E.g. recent `incoterm` field addition in ERPNext.
- Apps/fixtures can still specify exact fieldnames
* test: custom field naming
