mod_pubsub_serverinfo: Consider sibling vhosts 'connected' Prosody does not have s2s connections between vhosts. Multiple domains will therefor not show up as each-other 'remote domains'. With this commit, the module considers vhosts permanently s2s-connected. Additional debug logging has been added.

This module lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
modules_enabled = {
    -- other modules --
    "s2s_whitelist",

}
s2s_whitelist = {
    "example.org",
}
```