API: I can add a key with a userid@keybase.io (packet) that doesn't match my username

This is probably ok since its ignored if not matching, but might be a good idea to add a check to make sure and userid@keybase.io user id packet (if included) in key also matches the keybase username associated with an account (if only as a sanity check).

(Yeah, I am testing wierd scenarios.)

首先跟踪接受包含 userid@keybase.io 数据包的密钥的 API 路径，并确定数据包与账户用户名进行比较的位置。确认不匹配时的预期行为，然后添加覆盖，证明不一致的数据包会按决定被拒绝或忽略。完成标准是：在不破坏有效密钥的情况下强制执行健全性检查。

由索引模型根据 Issue 内容生成。