encrypt data at rest and in transit

[vigith]

          This is going to be a security concern.

The Authorization header is supposed to be only accessed by the client who initializes the request, and the server who receives the request, and it's encrypted during transmission. If we keep it and store it in ISB, that means the credential is leaked to and stored in a 3rd party.

Originally posted by @whynowy in https://github.com/numaproj/numaflow/pull/1578#discussion_r1531743310