hook_fullcalendar_editable is non-functional

Problem/Motivation

This issue was spun-off from 🐛 Hook not firing Active . It was noted that hook_fullcalendar_editable() is never invoked. A quick grep of the module's code show that there is neither an invokeAll() nor an alter() for this hook anymore. I didn't dig any deeper to see when it was lost, but given that hook_fullcalendar_process_dates_alter() was lost during the D8 upgrade it's a good bet that this happened at the same time.

Steps to reproduce

Build a module that invokes hook_fullcalendar_editable() or just run grep -r "fullcalendar_editable" ./ and note that the only place it appears in the code is in fullcalendar.api.php.

Proposed resolution

Either restore the functionality or delete hook_fullcalendar_editable() and hook_fullcalendar_editable_alter() from fullcalendar.api.php.

Remaining tasks

User interface changes

API changes

Data model changes