This commit adds remote cluster resource that specifies
connection and trust of the remote trusted cluster to the local
cluster. Deleting remote cluster resource deletes trust
established between clusters on the local cluster side
and terminates all reverse tunnel connections.
Migrations make sure that remote cluster resources exist
after upgrade of the auth server.
This commit introduced mutual TLS authentication
for auth server API server.
Auth server multiplexes HTTP over SSH - existing
protocol and HTTP over TLS - new protocol
on the same listening socket.
Nodes and users authenticate with 2.5.0 Teleport
using TLS mutual TLS except backwards-compatibility
cases.
This commit aadds multiplexer library of SSH/TLS on the same
listener socket. The multiplexer detects the protocol by the first
3 bytes of the incoming connection and forwards wrapped
connection either to the SSH ot TLS listeners.
The library also supports PROXY line protocol
and wraps connection information with connection details
from the proxy line received by the server