Who is Keith Davidson, the lawyer who negotiated hush money payments from Trump?

I figured if you went out and paid a whore then whatever you did was covered by Whore-Client Privilege. It prevents a them from testifying against his/her client. The purpose underlying this privilege is to ensure that clients receive competent service while preventing disclosure to family and friends without fear that the tryst will be revealed.
Or something like that - I ain't a pimp.