Convert dates in EJSON format / Access current processed field alias

[thomas_seres_panda (Thomas Sérès)]

Hi !
I would like to dynamically :

• match any fields corresponding to a format like "yyyy-MM-dd"
• add new field by using current processed field :
  example :
  add_field => { "[%{current_processed_field_name}'_ejson'][$date]" => "%{current_processed_field_value}" }

I need to do this to create a new field with a suffix to store dates as EJSON format.
Is there a way (an alias ?) to get current processed field name & value ?

What do you suggest ?

Thank you in advance !