-- migration_v2.1_group_invitations.sql
-- 主动邀请：团长/牧者直接邀请用户加入自己的小组
CREATE TABLE IF NOT EXISTS group_invitations (
  id INT AUTO_INCREMENT PRIMARY KEY,
  group_id INT NOT NULL,
  inviter_id INT NOT NULL,
  invitee_id INT NOT NULL,
  status ENUM('pending','accepted','declined','cancelled') NOT NULL DEFAULT 'pending',
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  handled_at TIMESTAMP NULL DEFAULT NULL,
  UNIQUE KEY uq_group_invitee (group_id, invitee_id),
  KEY idx_invitee (invitee_id, status)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;