[release-0.25] Set DLS namespace to object namespace before resolving DLS

[pierDipi]

If the namespace of the DLS on the broker or trigger
is not specified we can't resolve the DLS.

Note: I'm still investigating if this regression is present in
0.26 too, so I'm starting fixing this from the known broken
branch.

Reproducer:

---
apiVersion: v1
kind: Namespace
metadata:
  labels:
    bindings.knative.dev/include: "true"
  name: broker-v1-dlq
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: event-display
  namespace: broker-v1-dlq
spec:
  template:
    spec:
      containers:
      - image: quay.io/openshift-knative/knative-eventing-sources-event-display:v0.13.2
---
apiVersion: messaging.knative.dev/v1
kind: Channel
metadata:
  name: dlq-channel
  namespace: broker-v1-dlq
---
apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  name: broker
  namespace: broker-v1-dlq
spec:
  delivery:
    backoffDelay: PT1S
    backoffPolicy: linear
    deadLetterSink:
      ref:
        apiVersion: messaging.knative.dev/v1
        kind: Channel
        name: dlq-channel
    retry: 5
---
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: subscription
  namespace: broker-v1-dlq
spec:
  broker: broker
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: event-display
---
apiVersion: sources.knative.dev/v1
kind: SinkBinding
metadata:
  name: bind-heartbeat
  namespace: broker-v1-dlq
spec:
  subject:
    apiVersion: apps/v1
    kind: Deployment
    selector:
      matchLabels:
        app: heartbeat
  sink:
    ref:
      apiVersion: eventing.knative.dev/v1
      kind: Broker
      name: broker
  ceOverrides:
    extensions:
      sink: bound
---
apiVersion: eventing.knative.dev/v1beta1
kind: EventType
metadata:
  name: dev.knative.eventing.samples.heartbeat
  namespace: broker-v1-dlq
spec:
  type: dev.knative.eventing.samples.heartbeat
  source: https://knative.dev/eventing-contrib/cmd/heartbeats/#broker-v1/heartbeat
  broker: broker
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hearbeat
  namespace: broker-v1-dlq
  labels:
   app: heartbeat
   bindings.knative.dev/include: "true"
spec:
  selector:
    matchLabels:
      app: heartbeat
  template:
    metadata:
      labels:
        app: heartbeat
    spec:
      containers:
      - name: single-heartbeat
        image: quay.io/openshift-knative/knative-eventing-sources-heartbeats:v0.13.2
        args:
        - --period=1
        env:
        - name: POD_NAME
          value: heartbeat
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace

Output:

    - lastTransitionTime: "2021-11-15T08:19:19Z"
      message: channels.messaging.knative.dev "dlq-channel" not found
      reason: Unable to get the dead letter sink's URI
      status: "False"
      type: DeadLetterSinkResolved

Proposed Changes

• Set DLS namespace to object namespace before resolving DLS

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

Set DLS namespace to object namespace before resolving DLS.

Docs

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pierDipi

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [pierDipi]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-0.25@4b3c52f). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff               @@
##             release-0.25    #5903   +/-   ##
===============================================
  Coverage                ?   82.79%           
===============================================
  Files                   ?      200           
  Lines                   ?     6267           
  Branches                ?        0           
===============================================
  Hits                    ?     5189           
  Misses                  ?      748           
  Partials                ?      330           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4b3c52f...bef1ca3. Read the comment docs.

[pierDipi]

/cherry-pick release-0.26

This is a problem in 0.26 too.

[knative-prow-robot]

@pierDipi: once the present PR merges, I will cherry-pick it on top of release-0.26 in a new PR and assign it to you.

In response to this:

/cherry-pick release-0.26

This is a problem in 0.26 too.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/broker/trigger/trigger.go	88.5%	88.2%	-0.3

[pierDipi]

See #5906