Allow to add real guests

migration.sql

@@ -48,10 +48,10 @@ CREATE TABLE IF NOT EXISTS "trip" (
 );
 
 CREATE TABLE IF NOT EXISTS "user_trip" (
-	"user_id" INTEGER NOT NULL REFERENCES user(id),
+	"user_id" INTEGER REFERENCES user(id),
+	"user_note" text, -- only shown if user_id = none
 	"trip_details_id" INTEGER NOT NULL REFERENCES trip_details(id),
-	"created_at" text NOT NULL DEFAULT CURRENT_TIMESTAMP,
-	CONSTRAINT unq UNIQUE (user_id, trip_details_id) -- allow user to participate only once for each trip
+	"created_at" text NOT NULL DEFAULT CURRENT_TIMESTAMP
 );
 
 CREATE TABLE IF NOT EXISTS "log" (