validate connect block allowed only within group.service (fixes #9450)

[roccoblues]

This adds the missing validation mentioned in #9450 for a connect block to be allowed only in a group service.

[tgross]

Hi @roccoblues! Thanks for contributing this PR!

Unfortunately it doesn't look like this fixes the bug... I pulled this PR down locally and used the jobspec @shoenig provided in #9405

jobspec

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

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



    task "web" {
      driver = "docker"

      config {
        image = "hashicorpnomad/counter-api:v1"
      }

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

        # should only be valid in group level
        connect {
          sidecar_service {}
        }
      }
    }
  }
}

If I run that job, it passes validation and runs:

$ nomad version
Nomad v1.0.2-dev (2bccb85d38164cfee4bede21fa3d2b10d75a1985)

$ nomad job run ./example.nomad
==> Monitoring evaluation "205d603a"
    Evaluation triggered by job "countdash"
    Evaluation within deployment: "48b3bd4b"
    Allocation "588298bf" created: node "ebf7bb9b", group "api"
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "205d603a" finished with status "complete"

$ nomad alloc status 588
...

Recent Events:
Time                       Type        Description
2021-01-20T08:13:57-05:00  Started     Task started by client
2021-01-20T08:13:56-05:00  Task Setup  Building Task Directory
2021-01-20T08:13:55-05:00  Received    Task received by client

[roccoblues]

Hi @tgross,

yes you're right. The connect block was silently thrown away. Took me a while to step through the code and find the right place. I've fixed it now.

~/p/r/nomad (connect-block↑1|…) $ ./bin/nomad job run /tmp/example.job
Error submitting job: Unexpected response code: 500 (1 error occurred:
	* Task group api validation failed: 1 error occurred:
	* Task web validation failed: 1 error occurred:
	* 1 error occurred:
	* service "count-api" cannot have "connect" block, only services defined in a "group" block can
)

~/p/r/nomad (connect-block↑1|…) $ ./bin/nomad job validate /tmp/example.job
Job validation errors:
1 error occurred:
	* Task group api validation failed: 1 error occurred:
	* Task web validation failed: 1 error occurred:
	* 1 error occurred:
	* service "count-api" cannot have "connect" block, only services defined in a "group" block can

[tgross]

LGTM! Thanks @roccoblues!

[github-actions]

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