Provide sane default options for actions in Designer

PROBLEM

• In Designer, create an action in the Document Actions slot that is linked to a chain
• Chain only contains the Context.FetchDocument operation
• Deploy config in Web UI
• Trigger the action

=> Error 500 saying:

Caused by: org.nuxeo.ecm.automation.InvalidChainException: Cannot find any valid path in operation chain - no method found for operation 'Context.FetchDocument' and for first input type 'void'

EXPECTED

• Chain should be launched and executed by default without error when we create something in Designer
• We should provide consistent default configuration with what we do on Modeler side (default is to add a Context.FetchContextDocument operation)

TODO

• Keep input field optional (cannot be set as required, or it would not work if people try to launch a chain that has a void input)
• For new operations, set slot to document actions and input field to [[document]] by default