Make vault-upgrade-hook compatible to AEMaaCS

[ghenzler]

Since the package install hook event is not working for this use case, a content marker will have to be used (similar to what the implementation in Netcentric/accesscontroltool#405 does)

[kwin]

Which event is not working? We are talking here about mutable parts of the repository which are touched/upgraded/migrated only once. Obviously this package should be installed only when the right content is mounted in the AEM instance.

[tomasz-sobczyk]

Correct me if Im wrong but basically if we deploy this alongside a package containing mutable content we should be good to run groovies on mutable content just fine (obviously you should not try to modify /apps with a groovy script)

[kwin]

@tommix1987 The problem is that install hooks on mutable content packages are not supported (details in https://github.com/Netcentric/aem-cloud-validator#prevent-using-install-hooks-in-mutable-content-packages). Also the Groovy Console is currently not compatible with AEMaaCS either (CID15/aem-groovy-console#1