Adds a signal handler to this for signal.
Similar to [func@GObject.signal_connect], but the callback will only be run if this's
incoming messages headers (that is, the `request_headers`) contain a header named header.
| this |
a Message |
| header |
HTTP response header to match against |
| callback |
the header handler |
| signal |
signal to connect the handler to. |
| user_data |
data to pass to |
|
the handler ID from [func@GObject.signal_connect] |