consul/connect: support for proxy upstreams opaque config

[shoenig]

This PR adds support for configuring proxy.upstreams[].config for
Consul Connect upstreams. This is an opaque config value to Nomad -
the data is passed directly to Consul and is unknown to Nomad.

Closes #11392

[shoenig]

Spot check

modified countdash example

job "countdash" {
  datacenters = ["dc1"]

  group "api" {
    network {
      mode = "bridge"
    }

    service {
      name = "count-api"
      port = "9001"

      connect {
        sidecar_service {}
      }
    }

    task "web" {
      driver = "docker"

      config {
        image          = "hashicorpdev/counter-api:v3"
        auth_soft_fail = true
      }
    }
  }

  group "dashboard" {
    network {
      mode = "bridge"

      port "http" {
        static = 9002
        to     = 9002
      }
    }

    service {
      name = "count-dashboard"
      port = "9002"

      connect {
        sidecar_service {
          proxy {
            upstreams {
              destination_name = "count-api"
              local_bind_port  = 8080
              config { # new
                connect_timeout_ms = 9999
              }
            }
          }
        }
      }
    }

    task "dashboard" {
      driver = "docker"

      env {
        COUNTING_SERVICE_URL = "http://${NOMAD_UPSTREAM_ADDR_count_api}"
      }

      config {
        image          = "hashicorpdev/counter-dashboard:v3"
        auth_soft_fail = true
      }
    }
  }
}

Inspect service in Consul (contains upstream.config.connect_timeout_ms)

➜ curl -s localhost:8500/v1/agent/services | jq -r '.[] | select(.Service=="count-dashboard-sidecar-proxy") | .Proxy.Upstreams'
[
  {
    "DestinationType": "service",
    "DestinationName": "count-api",
    "LocalBindPort": 8080,
    "Config": {
      "connect_timeout_ms": 9999
    },
    "MeshGateway": {}
  }
]

[gulducat]

Assuming this is the extent of the required plumbing, LGTM!

Just a bit of food for thought and a clarifying question.

[github-actions]

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.