https://tracker.moodle.org/browse/MDL-75850 introduced the file redact service

Currently, these are all defined only in core (in the /files/clases/redactor/services) folder, with no apparent option to extend this (by plugin or callback)

https://github.com/moodle/moodle/blob/9242f9619ae6fb3881dbbc0c96030acd65ea5892/files/classes/redactor/manager.php#L97

It would be useful to be able to extend to add more file redaction types without submitting to core. An example would be PDF flattening and PDF js removal.