Add the support to install event sources

[houshengbo]

Problem
We cannot install any event resource available in https://github.com/knative/eventing-contrib.
Install the event sources available in the repo eventing-contrib. Make the CR able to configure the list of event sources, to be installed in the knative eventing.
The custom resource will look like this:

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeEventing
metadata:
  name: knative-eventing
  namespace: knative-eventing
spec:
  event-contrib:
    version: 0.12.1
    sources: github,kafka

We can use a comma separated string to specify all the event sources to be installed. Or use the following CR

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeEventing
metadata:
  name: knative-eventing
  namespace: knative-eventing
spec:
  event-contrib:
    version: 0.12.1
    sources:
      - github
      - kafka

Persona:
Which persona is this feature for?
Administrators.

Exit Criteria
A measurable (binary) test that would indicate that the problem has been resolved.

Time Estimate (optional):
How many developer-days do you think this may take to resolve?

Additional context (optional)
Add any other context about the feature request here.

[houshengbo]

We used to have a discussion on this feature: knative/eventing-operator#92

[matzew]

How does that relate to: #206 ??

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[houshengbo]

/reopen

[knative-prow-robot]

@houshengbo: Reopened this issue.

In response to this:

/reopen

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[houshengbo]

We can leverage the same model in knative serving CR, defining the ingress, to install an eventing source:

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeEventing
metadata:
  name: knative-eventing
  namespace: knative-eventing
spec:
  version: "0.22"
  eventingSource:
    github:
      enabled: true
      multiTenant: true

The field multiTenant: true is used to determine it is single or multi tenant. This field is available for github and kafkasource.

[houshengbo]

@evankanderson @maximilien
As we run into the issue of kustomize not recognizing the variable reference like !!merge <<: *openAPIV3Schema, it takes much effort for the operator to add the eventing source label, before saving the manifests under kodata. We decide to use a one source one directory approach to lower the bar of the implementation in operator.

The directory will be like:

[houshengbo]

The list of eventing sources includes:
AWS SQS: https://github.com/knative-sandbox/eventing-awssqs/releases/download/v0.23.0/awssqs.yaml,
ceph: https://github.com/knative-sandbox/eventing-ceph/releases/download/v0.23.0/ceph.yaml,
github: https://github.com/knative-sandbox/eventing-github/releases/download/v0.23.0/github.yaml,
kafka: https://github.com/knative-sandbox/eventing-kafka/releases/download/v0.23.0/source.yaml,
natss: https://github.com/knative-sandbox/eventing-natss/releases/download/v0.23.0/eventing-natss.yaml,
rabbitmq: https://github.com/knative-sandbox/eventing-rabbitmq/releases/download/v0.23.0/rabbitmq-source.yaml, prometheus: https://github.com/knative-sandbox/eventing-prometheus/releases/download/v0.23.0/prometheus-source.yaml,
redis: https://github.com/knative-sandbox/eventing-redis/releases/download/v0.23.0/redis-source.yaml,
gitlab: https://github.com/knative-sandbox/eventing-gitlab/releases/download/v0.23.0/gitlab.yaml, and
couchdb: https://github.com/knative-sandbox/eventing-couchdb/releases/download/v0.23.0/couchdb.yaml

[vaikas]

I think @antoineco might be interested in this as well and might have some ideas.