start with activity + fix tests

migration.sql

@@ -225,6 +225,15 @@ CREATE TABLE IF NOT EXISTS "distance" (
 );
 
 
+CREATE TABLE IF NOT EXISTS "activity" (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    text TEXT NOT NULL,
+    relevant_for TEXT NOT NULL,  -- e.g. user_id=123;trip_id=456
+    keep_until DATETIME
+);
+
+
 CREATE TRIGGER IF NOT EXISTS prevent_multiple_roles_same_cluster
 BEFORE INSERT ON user_role
 BEGIN