The attorney-client privilege is the foundation of the attorney-client relationship. CPLR 4503(a)(1) codifies the attorney-client privilege. It provides, in part: "Unless the client waives the privilege, an attorney or his or her employee, or any person who obtains without the knowledge of the client evidence of a confidential communication made between the attorney or his or her employee and the client in the course of professional employment, shall not disclose, or be allowed to disclose such communication … in any action, disciplinary trial or hearing …."