Register provider function for custom permission options
With $GLOBALS['TYPO3_CONF_VARS']['BE']['customPermOptions'] you can provide additional options that backend user groups can get assigned.
This is done in ext_tables and you have to provide an array of options. However if you want to involve database calls or other expensive operations to determine the available options, it would slow down the whole installation because it would be re-evaluated every time ext_tables is loaded.
It would be better to offer a way to register provider functions, that are only called when needed (in the backend form for backend user groups).
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