Implement automatic discovery for all soundtouch speaker in the home network

[syfds]

Currently only a manual entering the IP is possible to connect to a specific soundtouch speaker. It is not real intuitive for user with no base experience in networking.

Acceptance Critieria: There should be a possibility to scan the network for all soundtouch devices and list them all. So the user can choose the speaker and connect to it

Bose documentation: https://developer.bose.com/guides/bose-soundtouch-api/production-level-discovery Library: https://valadoc.org/avahi-gobject/index.htm

[syfds]

all speaker found by auto discovery are shown at the bottom in a separate panel