How to configure the signers in the Viafirma Documents templates to be used from Athento?

Athento allows the sending of a signature request (Viafirma Documents) through a template. This template must be correctly configured for its use. For this, all the template evidences cannot contain the characters "{" and "}" in the receiver ID, that is to say, they must be fixed identifiers. 

{{signer_1}}  # Incorrect

signer_1  # Correct

Once properly configured, the existing functionality in the document view can be used.