As a web admin I want to validate text fields that the visitors submit against custom Javascript functions that are only relevant to my own NRO.

The js functions will be added to the child theme by the NRO, and will have to return either "true" or an error message.

• In the EN forms, in the small pencil function, in text fields, add a text field with the label "JS validation callback fuction"
• If such a value exists for a field, when the field is submited, check if such a function is available in JS.
• If a function exists, pass to the function the value that was submited to the field
• If the function returns "true", submit the value
• If the function returns any text, show the text as error message.