Sunset gRPC Gateway

[jrschumacher]

With the addition of ConnectRPC #1524 we are sunsetting gRPC-gateway.

Impact:

• endpoints will no longer look like conventional REST endpoints, but gRPC in style
• the body of the requests will take the form as defined in the protos
• GET requests may not be available

Benefits:

• testing and maintenance of endpoints is reduced significantly
• generated SDKs can make use of the HTTP endpoints if required

Caveats:

• we will continue to maintain legacy KAS endpoints to make sure interoperability

[jrschumacher]

@dmihalcik-virtru I know we need to maintain the rewrap endpoint, but do we need to maintain the public key endpoint? If older SDKs want to protect data, it seems that they should use the newer endpoints...