Add event and event series entities

[pacodelcastillolopez]

Adding two new ANET entities: event series and events.

• They have a host organization that can be any organization in ANET and an admin organization which needs to be managed by the user creating the event series or event (superuser or admin).
• Events have also a location, start date and end date and are searchable.
• Objectives can be linked to events.
• Reports can be associated to events. When creating from the Event page it will inherit its location and objectives, the date of the report has to be within the start and end date of the event.
• Events will be displayed in the organization and location pages.

To do:

• Add testing once implementation is approved.
• Add blocking feature (flag in an event that can block a location for the period the event takes place)
• Add attachments to events (will be done together with adding avatar to events)

Closes AB#1064

User changes

• Can search for events in ANET.
• Can associate a report to an event.

Superuser changes

• Can create event series and events managed by the organizations they manage.
• Can see the event series and events they manage under "My Events".

Admin changes

• Can create event series and events managed by any organization.

System admin changes

• anet.yml or anet-dictionary.yml needs change
• db needs migration
• documentation has changed
• graphql schema has changed

Checklist

• Described the user behavior in PR body
• Referenced/updated all related issues
• commits follow a repo#issue: Title title format and these 7 rules
• commits have a clean history, otherwise PR may be squash-merged
• Added and/or updated unit tests
• Added and/or updated e2e tests
• Added and/or updated data migrations
• Updated documentation
• Resolved all build errors and warnings
• Opened debt issues for anything not resolved here

[azure-boards]

✅ Successfully linked to Azure Boards work item(s):

• Issue 1064

[gjvoosten]

Maybe use different colours for the different types of events, like for reports, where we have:

        classNames: [`event-${Report.getStateForClassName(r)}`],

?