Drag & drop functionality

Problem/Motivation

As a content administrator I want to drag and drop events on the calendar view to update their starting datetime.

Steps to reproduce

• Create a month Calendar View
• Enable Drag&Drop functionality
• As a use with sufficient permissions, drag and drop an event on the calendar view

Proposed resolution

• Create a new submodule to hold all the logic of the Drag & Drop functionality
• Use the HTML Drag & Drop API
• Edit the calendar view table with relevant HTML attributes
• Find the most agnostic solution for a route / API to receive the drag&drop event's data (e.g. to update the event on drop)

Remaining tasks

User interface changes

API changes

Data model changes