kamelets: support for kamelet local beans

[lburgazzoli]

Route Template local beans is approaching and we need to define how we can leverage such functionality in camel-k and in the kamelets definition.

The current layout for kamelets is:

apiVersion: camel.apache.org/v1alpha1
kind: Kamelet
metadata:
  name: telegram-text-source e"
spec:
  ...
  flow: 
    from:
      uri: direct:start
      steps:
         ...

I'd propose to replaces flow with template so it would looks like:

apiVersion: camel.apache.org/v1alpha1
kind: Kamelet
metadata:
  name: telegram-text-source e"
spec:
  ...
  template: 
    beans:
      - name: myBean
        type: com.acme.MyBean
        properties:
         foo: "bar"
    from:
      uri: direct:start
      steps:
        - process: "myBean"

NOTE:

• we should keep flow for backward compatibility but to create template local beans one has to use template keyword.
• the new template keyword can be provided by the Camel YAML DSL so we can reduce the custom code we have to maintain for camel-k.

The code generated by the camel-k operator should then be:

- template: 
    beans:
      - name: myBean
        type: com.acme.MyBean
        properties:
         foo: "bar"
    from:
      uri: direct:start
      steps:
        - process: "myBean"

[lburgazzoli]

/cc @nicolaferraro
/cc @davsclaus
/cc @heiko-braun

[lburgazzoli]

Relates to https://issues.apache.org/jira/browse/CAMEL-16584

[davsclaus]

Yeah then the beans part of the template can then use the new local bean bind in camel-core (Camel 3.10 - CAMEL-16584). Then that bean myBean is local and only available while the template is creating routes. And each route will have its own instance that bean created.

The route template DSL in camel-core-model, does not however have beans, but its a novel idea, we could consider adding that, which allow this to be done in a more general and vanilla fashion with camel-core for all runtimes (not a special syntax in camel-k).

[lburgazzoli]

The route template DSL in camel-core-model, does not however have beans, but its a novel idea, we could consider adding that, which allow this to be done in a more general and vanilla fashion with camel-core for all runtimes (not a special syntax in camel-k).

yep absolutely true, the goal is to have it also in the XML DSL at some point.