Phase 2: Subsonic REST API framework (auth, response formatting, error handling, routing) plus user permission model

internal/subsonic/system.go

@@ -0,0 +1,19 @@
+package subsonic
+
+func init() {
+	register("ping", handlePing)
+	register("getLicense", handleGetLicense)
+}
+
+func handlePing(rc *Context) *apiError {
+	rc.Response = newResponse()
+	return nil
+}
+
+// handleGetLicense always reports a valid, unlimited license: VibeSonic
+// is free software and never requires a commercial Subsonic license.
+func handleGetLicense(rc *Context) *apiError {
+	rc.Response = newResponse()
+	rc.Response.License = &License{Valid: true}
+	return nil
+}