As a result of work on #issue #1151 and discussion in https://github.com/tigase/tigase-server/pull/32#discussion_r432540717 it came to light that our current handling of VHost configuration and it's defaults is lacking:

1. It's impossible to specify whether our domain should use it's configuration or defaults (in 8.1.0 some configurations, especially with list of options, allowed to select default, but others assumed that lack of entry resulted in using default configuration; this was especially problematic with boolean configurations)
2. It's impossible to enforce basic system defaults/minimums using default VHost configuration (for example we would like to enforce that all domains have to use TLS and it won't be possible to disable it in domain configuration)