This PR adds the capability of running Connect Native Tasks on Nomad,
particularly when TLS and ACLs are enabled on Consul.
The `connect` stanza now includes a `native` parameter, which can be
set to the name of task that backs the Connect Native Consul service.
There is a new Client configuration parameter for the `consul` stanza
called `share_ssl`. Like `allow_unauthenticated` the default value is
true, but recommended to be disabled in production environments. When
enabled, the Nomad Client's Consul TLS information is shared with
Connect Native tasks through the normal Consul environment variables.
This does NOT include auth or token information.
If Consul ACLs are enabled, Service Identity Tokens are automatically
and injected into the Connect Native task through the CONSUL_HTTP_TOKEN
environment variable.
Any of the automatically set environment variables can be overridden by
the Connect Native task using the `env` stanza.
Fixes#6083
Promote the Connect ACLs guide on the jobspec connect stanza docs
page. This was suggested in a ticket after someone got stuck not
realizing they needed to enable Consul Intentions for their connect
enabled services, which is covered in the guide.
Replace the existing top example with something that is directly
runnable on a `-dev-connect` nomad setup.
Add the _complete_ `countdash` example at the bottom in the
examples section, so that people do not need to go guide-hunting
to find a complete example. The hope is people will see more
runnable examples and be less afraid of connect.
