prefix: friend.friendHandler

sendFriendRequest(fid: int): (code: Code.OK, msg: "Friend request sent successfully.") // 发送好友请求
acceptFriendRequest(fid: int): (code: Code.OK, msg: "Friend request accepted successfully.") // 接受好友请求
getFriendList(): (code: Code.OK, friendList: friend_list) // 获取好友列表
addToBlackList(bid: int): (code: Code.OK, msg: "User added to blacklist successfully.") // 将用户加入黑名单
removeFromBlackList(bid: int): (code: Code.OK, msg: "User removed from blacklist successfully.") // 将用户从黑名单中移除
getBlackList(): (code: Code.OK, blackList: black_list) // 获取黑名单
getPendingFriendRequests(): (code: Code.OK, friendRequests: friend_requests) // 获取待处理的好友请求
getPendingFriendInvitations(): (code: Code.OK, friendInvitations: friend_invitations) // 获取待处理的好友邀请