Retention rules - Expose flexible retention during edit

As a records manager, I can edit a rule that leverages flexible retention

AC
When editing a retention rule
The checkbox related to the "Allow undeclaring the record" exposes the current value of the retention_rule:flexibleRecords property

• checked if property is set to true
• unchecked if property is set to false

If the property value is changed during edit, the new value is set in the retention_rule:flexibleRecords property for the document

• true if checkbox is checked
• false if checkbox is unchecked