new: add ability for caller to get back received raw *nats.Msg to a channel

[aaslamin]

Issue: https://github.com/aporeto-inc/aporeto/issues/1274

This PR introduces a new option to the NATS pubsub Publish method: NATSOptRespondToChannel

This option allows clients to receive the response *Publication to a channel they configure when using the NATS request-reply messaging pattern. This is particularly useful in situations where the client is publishing something within an HTTP handler and they need to block and wait for a reply so they can use the response message to craft an appropriate HTTP response (e.g. Aporeto automations handling webhooks!).

Sample usage:

	responseCh := make(chan *Publication)
	errorCh := make(chan error)

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	go func() {
		if err := p.pubsub.Publish(pub, bahamut.NATSOptRespondToChannel(ctx, responseCh)); err != nil {
			errorCh <- err
		}
	}()

	select {
	case response := <-responseCh:
		fmt.Printf("received a message: %+v\n", response)
	case err := <-errorCh:
		fmt.Printf("received an error: %+v\n", err)
	}

Other things

• This option is backwards compatible with existing logic.
• New unit tests added ✅

---

👀Review: @primalmotion @t00f

[primalmotion]

I think it would be more symetrical to return a publication in response

[aaslamin]

I think it would be more symetrical to return a publication in response

Yeah, you're right because the only thing you can publish right now is a Publication. Good catch, I will make that change.

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "",
    "component": "bahamut",
    "pr-id": "56",
    "commit-sha": "30acc338353db9accc27c0657ce1d0c31e9ecc32"
  }
]

[codecov]

Codecov Report

Merging #56 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   88.27%   88.35%   +0.07%     
==========================================
  Files          28       28              
  Lines        2107     2121      +14     
==========================================
+ Hits         1860     1874      +14     
  Misses        220      220              
  Partials       27       27

Impacted Files	Coverage Δ
pubsub_nats_options.go	100% <100%> (ø)	⬆️
pubsub_nats.go	51.85% <100%> (+3.85%)	⬆️

---

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[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "",
    "component": "bahamut",
    "pr-id": "56",
    "commit-sha": "2b1f06eca20102727c3d66247fdc2fc1cb2e50e9"
  }
]

[aaslamin]

Update @primalmotion

• A response will be sent to the response channel if and only if the raw *nats.Msg could be decoded into a Publication, otherwise an error is returned - 201a564
• Another unit test added to cover the new behaviour - 2b1f06e

[aaslamin]

👀

[primalmotion]

LGTM. please run a test of the backend with this

Edit: oh you did
Edit 2: oh no you did not
Edit 3: actually we need a full ft in here

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "",
    "component": "bahamut",
    "pr-id": "56",
    "commit-sha": "2b1f06eca20102727c3d66247fdc2fc1cb2e50e9"
  },
  {
    "project": "",
    "component": "backend",
    "pr-id": "408",
    "commit-sha": "6f3c24caaae0e91a09c4257d22a410299978dccd"
  }
]

[aporeto-bot]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "receive-publish-response",
    "component": "bahamut",
    "pr-id": "56",
    "commit-sha": "2b1f06eca20102727c3d66247fdc2fc1cb2e50e9"
  },
  {
    "project": "receive-publish-response",
    "component": "backend",
    "pr-id": "408",
    "commit-sha": "6f3c24caaae0e91a09c4257d22a410299978dccd"
  }
]

[primalmotion]

ft failed on a unrelated unstable test. merging