The actions to run synchronously can be configured via the `execute_sync`
configuration key.
Executing an action synchronously means that SFTPGo will not return a result
code to the client until your hook have completed its execution.
Fixes#409
HTTP clients are used for executing hooks such as the ones used for custom
actions, external authentication and pre-login user modifications.
This allows, for example, to use self-signed certificate without defeating the
purpose of using TLS
The HTTP notifications are now invoked as POST and the notification is
a JSON inside the POST body.
This is a backward incompatible change but this way the actions can be
extended more easily, sorry for the trouble
Fixes#101