* Use Teleport's standard buildbox
This commit edits the teleport-operator container image build process to
rely on Teleport's standard buildbox. This will make sure we are using a
single go version at all time.
This also removed unused environment variables from
`operator/Makefile`.
* Extract BUILDBOX variables out of build.assets/Makefile
* Put `teleport-operator` bin out of the Teleport source volume
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.