Allow binding to IP on IRC

Add configuration option "Bind" that is passed on to girc, allowing
to choose which IP address to use on systems that have multiple ones.

bridge/irc/irc.go

@@ -308,6 +308,7 @@ func (b *Birc) getClient() (*girc.Client, error) {
 		User:       user,
 		Name:       realName,
 		SSL:        b.GetBool("UseTLS"),
+		Bind:       b.GetString("Bind"),
 		TLSConfig:  &tls.Config{InsecureSkipVerify: b.GetBool("SkipTLSVerify"), ServerName: server}, //nolint:gosec
 		PingDelay:  pingDelay,
 		// skip gIRC internal rate limiting, since we have our own throttling

matterbridge.toml.sample

@@ -34,6 +34,11 @@ UseSASL=false
 #OPTIONAL (default false)
 SkipTLSVerify=true
 
+#Local address to use for server connection
+#Note that Server and Bind must resolve to addresses of the same family.
+#OPTIONAL (default "")
+Bind=""
+
 #If you know your charset, you can specify it manually.
 #Otherwise it tries to detect this automatically. Select one below
 # "iso-8859-2:1987", "iso-8859-9:1989", "866", "latin9", "iso-8859-10:1992", "iso-ir-109", "hebrew",