Add Kafka Source defaults, starting with KEDA annotations

[lionelvillard]

Proposed Changes

• Add new config-kafka-source-defaults configmap to be used by the defaulting mutating webhook
• When autoscaler is enabled in the configmap, the defaulting webhook automatically adds KEDA annotations.

Release Note

- 🎁Autoscaling annotations can now be automatically added to KafkaSource objects. See the documentation for more details. 

Docs
See knative/docs#4181

/cc @steven0711dong @matzew @zroubalik

[knative-metrics-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/apis/sources/config/kafka_defaults.go	Do not exist	84.2%
pkg/apis/sources/config/store.go	Do not exist	93.8%

[codecov]

Codecov Report

Merging #855 (a295d55) into main (75b06f9) will decrease coverage by 0.50%.
The diff coverage is 81.08%.

@@            Coverage Diff             @@
##             main     #855      +/-   ##
==========================================
- Coverage   75.14%   74.64%   -0.51%     
==========================================
  Files         139      143       +4     
  Lines        6442     6633     +191     
==========================================
+ Hits         4841     4951     +110     
- Misses       1369     1435      +66     
- Partials      232      247      +15     

Impacted Files	Coverage Δ
pkg/apis/sources/config/kafka_defaults.go	68.42% <68.42%> (ø)
pkg/apis/sources/config/store.go	92.00% <92.00%> (ø)
pkg/apis/sources/v1beta1/kafka_defaults.go	100.00% <100.00%> (ø)
pkg/source/adapter/adapter.go	54.73% <0.00%> (-3.70%)	⬇️
...rce/reconciler/source/resources/receive_adapter.go	96.51% <0.00%> (-3.49%)	⬇️
pkg/source/adapter/message.go	72.72% <0.00%> (-1.60%)	⬇️
pkg/source/mtadapter/adapter.go	46.61% <0.00%> (-1.22%)	⬇️
cmd/channel/post-install/main.go	0.00% <0.00%> (ø)
... and 2 more

---

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[steven0711dong]

Was this tested? I just deployed this change into pg1 and created a Kafka source from there. The annotations were not added.

[lionelvillard]

Was this tested? I just deployed this change into pg1 and created a Kafka source from there. The annotations were not added.

yes. What is pg1 :-) ?

Anyway, did you change the configmap to enable annotations injection?

[steven0711dong]

lgtm

[steven0711dong]

/lgtm

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lionelvillard, steven0711dong

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• OWNERS [lionelvillard,steven0711dong]

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[lionelvillard]

/cherry-pick release-0.25

[knative-prow-robot]

@lionelvillard: #855 failed to apply on top of branch "release-0.25":

Applying: add Kafka defaults, starting with KEDA annotations
.git/rebase-apply/patch:998: new blank line at EOF.
+
warning: 1 line adds whitespace errors.
Using index info to reconstruct a base tree...
M	pkg/apis/sources/v1beta1/kafka_defaults.go
M	pkg/apis/sources/v1beta1/kafka_defaults_test.go
M	vendor/modules.txt
Falling back to patching base and 3-way merge...
Auto-merging vendor/modules.txt
Auto-merging pkg/apis/sources/v1beta1/kafka_defaults_test.go
CONFLICT (content): Merge conflict in pkg/apis/sources/v1beta1/kafka_defaults_test.go
Auto-merging pkg/apis/sources/v1beta1/kafka_defaults.go
CONFLICT (content): Merge conflict in pkg/apis/sources/v1beta1/kafka_defaults.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 add Kafka defaults, starting with KEDA annotations
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-0.25

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