Add new command: event createrole

[JobDoesburg]

Name

Invoke with, for example, !event createrole 123, where 123 is the event-id in concrexit.

Description

The command should create a new role and assign it to everyone registered for the event (in concrexit). This role can then be used for event-specific event channels.

Additionally, !event removerole 123 should remove it again and !event roleinfo 123 should return everyone who has registered for the event (as well as a list of people who are registered but do not have a discord account connected)

Use cases

Online events

Permissions

Ideally: people that are organizer of the event

Additional context

The name of the role can be the event name.

[se-bastiaan]

I think it would be best to do this as follows:

1. Any committee member can execute this command, if they are part of the organising group of the event we continue
2. That we activated the role itself needs to be saved somewhere, because it should be part of the state when syncing.
3. We also create a command !event createcategory/removecategory which adds a category to the Discord with the name of the event. The organisers of the event get full edit permission of this category and will thus be allowed to complete manage their event within this category.

[mark-boute]

I think we should also remove a role a day after an event has ended during a sync.