CREATE TABLE IF NOT EXISTS user_roles (
  user_id INTEGER NOT NULL,
  project_id INTEGER NOT NULL,
  p_role TEXT NOT NULL, -- 'project_manager' or 'member'
  FOREIGN KEY (user_id) REFERENCES users (id)
  FOREIGN KEY (project_id) REFERENCES projects (id)
  FOREIGN KEY (p_role) REFERENCES project_role (p_role)
  PRIMARY KEY (user_id, project_id)
);