Possibility to create an automation chain that accepts other input than document, documents

In some cases we need to have automation chains that accepts inputs that are not doucment or list of documents. For example, when defining a new contrib to the import service. This service call an automation with an the bloblist as input. It's not possible to get this input in a Studio automation chain as the user interface refuse to save.

=> Remove the validation check that makes sure the chain start with a document/documents in input.