Let the Data Transfer Object print keys of associative arrays
Problem/Motivation
For various scenarios, especially identified while developing #3276448: eca_form: Feature clarification, printing out the according keys of an associative array may be useful when printing out a list. For example, one might want to print out submitted form values, where the keys would identify the form field inputs.
Steps to reproduce
Proposed resolution
Extend the DTO's string representation in the way that it's automatically printing out the keys when it holds an associative array.
Remaining tasks
User interface changes
API changes
Data model changes
Edited by drupalbot