Add MDNS/avhai service autodiscovering

[mStirner]

I thought about a "auto discovering", of the (slave) devices.
For that i created 2 files in /etc/avahi/services/:

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name replace-wildcards="yes">Modbus Slave 1 (Klimaanlage)</name>
  <service>
    <type>_modbus._tcp</type>
    <port>502</port>
    <txt-record>slave_id=1</txt-record>
    <txt-record>device=Klimaanlage</txt-record>
  </service>
</service-group>

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name replace-wildcards="yes">Modbus Slave 2 (Stromzaehler)</name>
  <service>
    <type>_modbus._tcp</type>
    <port>502</port>
    <txt-record>slave_id=2</txt-record>
    <txt-record>device=Stromzaehler</txt-record>
  </service>
</service-group>

Any thoughts about, to create such file while installing/building?
I know, that its up to the end user to fill in the correctly IDs/slaves etc.

But why not advertise the service regardless?