Connection required on initialization

When instantiating a `GitHub::Ldap` object, a connection is established and query performed to determine the server's capabilities which are used to configure the appropriate membership search strategies.

I'd like to avoid having to connect and query on object instantiation and only perform the query when it's absolutely needed.

从 GitHub::Ldap 对象初始化开始，跟踪选择成员搜索策略的连接和服务器能力查询。确定哪些操作确实需要这些能力，然后验证初始化会避免建立连接，同时所需的成员搜索仍能获取正确的策略并查询服务器。

由索引模型根据 Issue 内容生成。