Add admin configuration page for event default layout settings

Development
1

## Problem Statement
Currently, when creating a new event in Indico, the navigation bar
is displayed by default. However, some institutions may prefer to
hide the navigation bar by default for a cleaner interface. Event
managers must manually disable it for each new event.

Current Behavior

  • New events have `show_nav_bar` set to `True` by default
  • Event managers must manually disable it for each new event
  • There is no way for system administrators to change this global default
  • This is inconvenient for institutions that rarely use the navigation bar

Desired Behavior

Add a configuration page in the Indico system administration interface
that allows administrators to set default values for event layout settings,
including but not limited to:

  • `show_nav_bar` (default: True)
  • `show_banner` (default: False)
  • `show_social_badges` (default: True)
  • Other layout-related settings
2

You can do that from a (custom) plugin. Hook into the event created signal and set the event setting based on a global plugin setting.

While I generally love lots of configurability as a user, I don’t think adding default for such specific things is a good idea. There can be too much configurability as well…