mod_http_oauth2: Improve error messages for URI properties Since there are separate validation checks for URI properties, including that they should use https, with better and more specific error reporting. Reverts 'luaPattern' to 'pattern' which is not currently supported by util.jsonschema, but allows anything that retrieves the schema over http to validate against it, should they wish to do so.

Over the years, some servers stop working for various reasons, and leave
behind broken roster subscriptions that trigger failing s2s connections.
This module allows cleaning up such cases by unsubscribing local users
from their contacts on those servers. Also works for typos and the like.
Use with care.

```lua
Component "gmail.com" "unsubscriber"
```