fix(session): allow providers without default URL

internal/app/session/session.go

@@ -153,7 +153,13 @@ func RegisterDefaults() {
 
 // ApplyAuthDefaults fills in Engine and URL from the auth provider when they are not set explicitly.
 // For -auth none the fields are left untouched (the caller supplies them directly).
-// Returns an error if the auth provider has no default URL and -url was not given.
+//
+// An empty cfg.URL is acceptable when the auth provider does not advertise a
+// DefaultServiceURL — those providers (e.g. jitsi) extract the SFU host from
+// the user-supplied RoomURL inside Issue(), so an externally fixed
+// service URL would be meaningless. Providers that DO advertise a
+// DefaultServiceURL (telemost, wbstream, jazz) still require URL to be set
+// when their default cannot be applied.
 func ApplyAuthDefaults(cfg Config) (Config, error) {
 	if cfg.Auth == authNone || cfg.Auth == "" {
 		return cfg, nil
@@ -168,7 +174,7 @@ func ApplyAuthDefaults(cfg Config) (Config, error) {
 	if cfg.URL == "" {
 		cfg.URL = p.DefaultServiceURL()
 	}
-	if cfg.URL == "" {
+	if cfg.URL == "" && p.DefaultServiceURL() != "" {
 		return cfg, fmt.Errorf("%w: auth provider %q has no default URL", ErrURLRequired, cfg.Auth)
 	}
 	return cfg, nil

internal/engine/jitsi/jitsi.go

@@ -27,6 +27,7 @@ import (
 
 	"github.com/openlibrecommunity/olcrtc/internal/engine"
 	"github.com/openlibrecommunity/olcrtc/internal/logger"
+	pioninterceptor "github.com/pion/interceptor"
 	"github.com/pion/webrtc/v4"
 	"github.com/zarazaex69/j"
 )
@@ -238,7 +239,20 @@ func (s *Session) videoTrackHandler() func(*webrtc.TrackRemote, *webrtc.RTPRecei
 func (s *Session) negotiatePC(ctx context.Context, jSess *j.Session) error {
 	settings := webrtc.SettingEngine{}
 	settings.LoggerFactory = logger.NewPionLoggerFactory()
-	api := webrtc.NewAPI(webrtc.WithSettingEngine(settings))
+
+	// pion auto-registers a default interceptor chain (sender reports,
+	// receiver reports, NACK, etc.) when none is supplied. Several of
+	// those probe the DTLS transport on a tick — until DTLS comes up
+	// (which can take seconds against Jitsi's STUN-only path, or never
+	// in pathological cases) they spam logs with
+	// "the DTLS transport has not started yet". JVB performs its own
+	// RTCP feedback aggregation, so the conference PC does not need
+	// any of those interceptors. An empty registry silences the noise.
+	registry := &pioninterceptor.Registry{}
+	api := webrtc.NewAPI(
+		webrtc.WithSettingEngine(settings),
+		webrtc.WithInterceptorRegistry(registry),
+	)
 
 	// Jicofo emits Plan B style SDP with separate <content> sections per
 	// media kind and SSRC-keyed source descriptors. pion's default