Run and Hook sockets over TLS with token authorization for CAAS

[hpidcock]

Run and Hook sockets over TLS with token authorization for CAAS

Adds encryption and authentication to CAAS juju-run and jujuc connections.

• juju-run multiplex server listens on TCP+TLS
• juju-run local listener per uniter on unix socket
• jujuc listener per hook context either over TCP+TLS or unix socket
• x509 certificates generated by apiserver on request from
  caasoperatorprovisioner and injected into operator config map
• juju-run auth token generated per unit and store in operator.yaml alongside
  ca.crt file (controller's CA cert)
• jujuc listner pass token via hook env vars & ca cert filename passed
  by env var
• caasoperatorprovisioner updates existing operators with certificates
• increase rsa key size to 3072 bits to future proof past 2030

QA steps

make microk8s-operator-update
export JUJU_DEV_FEATURE_FLAGS=developer-mode
juju bootstrap microk8s
juju deploy cs:~juju/redis-k8s-1

$ juju exec --unit redis-k8s/0 hostname
redis-k8s-645fdf557-hrkcm
$ juju exec --unit redis-k8s/0 status-set active "hello from unit"
$ juju status | grep redis-k8s/0
redis-k8s/0*  active    idle   10.1.1.20  6379/TCP  hello from unit
$ microk8s.kubectl --namespace controller-microk8s-localhost exec redis-k8s-645fdf557-hrkcm -- juju-run redis-k8s/0 "status-set active 'hello from unit via juju-run on the unit'"
$ juju status | grep redis-k8s/0
redis-k8s/0*  active    idle   10.1.1.20  6379/TCP  hello from unit via juju-run on the unit

$ juju exec --unit redis-k8s/0 --operator hostname
redis-k8s-operator-0
$ juju exec --unit redis-k8s/0 --operator status-set active "hello from operator"
$ juju status | grep redis-k8s/0
redis-k8s/0*  active    idle   10.1.1.20  6379/TCP  hello from operator
$ microk8s.kubectl --namespace controller-microk8s-localhost exec redis-k8s-operator-0 -- juju-run redis-k8s/0 "status-set active 'hello from unit via juju-run on the operator'"
$ juju status | grep redis-k8s/0
redis-k8s/0*  active    idle   10.1.1.20  6379/TCP  hello from unit via juju-run on the operator

Documentation changes

N/A

Bug reference

https://bugs.launchpad.net/juju/+bug/1837841

[wallyworld]

Looks good, thanks!

[hpidcock]

$$merge$$

[hpidcock]

$$merge$$