Add support for sinkbinding

[nicolaferraro]

Fix #1548

Requires: apache/camel-k-runtime#411

Tasks:

• Add sinkbinding option in knative trait
• Implement scenario 2 in the issue
• E2E tests
• Regen docs

Release Note

Standard integrations can now create a sinkbinding to be listed as Knative sources

[heiko-braun]

@nicolaferraro do you have an example of a sinkbinding declaration with a regular integration?

[nicolaferraro]

@nicolaferraro do you have an example of a sinkbinding declaration with a regular integration?

@heiko-braun this is an (working) integration that results as a regular Knative source:

apiVersion: camel.apache.org/v1
kind: Integration
metadata:
  name: source
spec:
  flows:
  - from:
      uri: timer:tick
      parameters:
        period: "1000"
      steps:
      - set-body:
          constant: Hello SinkBinding !!!
      - transform:
          simple: ${body.toUpperCase()}
      - to: log:info
        # the following line may also be split into k/v format (to be implemented)
      - to: knative:channel/messages?apiVersion=messaging.knative.dev/v1beta1&kind=InMemoryChannel
  traits:
    knative:
      configuration:
        sinkBinding: true # we may default it to true in the future to avoid this setting

A future simplified version may look like:

apiVersion: camel.apache.org/v1
kind: Integration
metadata:
  name: source
spec:
  flows:
  - from:
      uri: timer:tick
      parameters:
        period: "1000"
      steps:
      - set-body:
          constant: Hello SinkBinding !!!
      - transform:
          simple: ${body.toUpperCase()}
      - to: log:info
      - to:
          uri: knative:endpoint
          parameters:
            apiVersion: messaging.knative.dev/v1beta1
            kind: InMemoryChannel
            name: messages

Which is very close to the equivalent CamelSource (current working implementation):

apiVersion: sources.knative.dev/v1alpha1
kind: CamelSource
metadata:
  name: source
spec:
  source:
    flow:
      from:
        uri: timer:tick
        parameters:
          period: "1000"
        steps:
        - set-body:
            constant: Hello Old CamelSource !!!
        - transform:
            simple: ${body.toUpperCase()}
        - to: log:info
  sink:
    ref:
      apiVersion: messaging.knative.dev/v1beta1
      kind: InMemoryChannel
      name: messages