Stream module: DTLS support for UDP listeners

Stream module: DTLS support for UDP listeners: a task in LegoFlow-SWE (Harbor dataset). The stream module currently does not allow ssl and udp to be combined in a listen directive, which prevents setting up DTLS-based secure UDP services. Additionally, the ssl protocols directive does not accept…

The task

The stream module currently does not allow `ssl` and `udp` to be combined in a `listen` directive, which prevents setting up DTLS-based secure UDP services. Additionally, the `ssl_protocols` directive does not accept `dtlsv1` or `dtlsv1.2` as valid protocol values.

Part of Lego-X/LegoFlow-SWE.