we are basically coming from here:
owncloud/updater#217 (comment)

So in CLI mode the new updater can easily execute occ and process it's json output. No brainer.

But in the web based updater ui we cannot rely on being allowed to spawn off the occ cli tool.

So from my understanding we need a way to execute some/all occ commands via web requests.

Something like

POST https://domain.tld/owncloud/index.php/occ/app:list?format=json

Access should be limited - e.g. by using a shared key/secret between the updater and the owncloud instance by placing a commonly used file into config or data dir.

This could also be used to by pass maintenance mode checks - if necessary.

@VicDeo @karlitschek @PVince81 @LukasReschke fire your 🔫s and throw your 💣s and 🔪s at these ideas. THX