MM-11693 Allow connections to /plugins for interactive message buttons. (#9333)

* Allow connetions to /plugins for interactive message buttons.

* Adding siteurl to exclusions for AllowedUntrustedInternalConnections

* Adding subpath support for allowing interactive message buttons plugin connections.

utils/httpclient.go

@@ -52,7 +52,7 @@ func init() {
 
 type DialContextFunction func(ctx context.Context, network, addr string) (net.Conn, error)
 
-var AddressForbidden error = errors.New("address forbidden")
+var AddressForbidden error = errors.New("address forbidden, you may need to set AllowedUntrustedInternalConnections to allow an integration access to your internal network")
 
 func dialContextFilter(dial DialContextFunction, allowHost func(host string) bool, allowIP func(ip net.IP) bool) DialContextFunction {
 	return func(ctx context.Context, network, addr string) (net.Conn, error) {