Lazy app config values may still be loaded on every request

[juliusknorr]

On setups with LDAP or other cases where getKeys is used the lazy app config is basically ignored and we fetch the full table

server/lib/private/AppConfig.php

Line 99 in c7037d7

$this->loadConfigAll($app);

This may lead to larger amount of data being transferred on every request from the database and being hold in memory for each request:

For the impact, on our instance we have a config value that is 8MB in size which is needed on every request. With 250 concurrent requests this is an additional demand of 2GB for the server.

cc @ArtificialOwl @sorbaugh

[ArtificialOwl]

can we store all configs in a single config entry ?
or loop on a prefix+increment using hasKey() ?