Recording post-processing

[defnull]

Allow to intercept recording import and manipulate recordings before they are imported, e.g. to generate subtitles, censor chat messages, fix playback issues or re-encode media files.

Proposal:
Introduce a new config option called RECORDING_IMPORT_HOOK. If defined, it should point to an executable that is called once per playback format at an early stage during import.

The hook script is called without parameters, but with the current working directory pointing to a temporary folder that contains extracted recording data. The script is allowed to reads or manipulate any files within that directory, including metadata.xml or media files. If the script finishes successfully, then the import will continue as usual. If the script fails, the import will also fail. All output will be logged.