Reject this certificate, asynchronously.
Before calling this method, you must call add_rejection at least once, to set the reason(s) for rejection (for instance, a certificate might be both self-signed and expired).
In or after callback, you may call reject_async.end to check the result.
notify::state will also be emitted when the connection manager signals that the certificate has
been rejected.
| this |
a TLS certificate |
| callback |
called on success or failure |
| user_data |
user data for the callback |