Add a "my events" page

[TomNaessens]

Add a "my events" page where signed in users can see an overview of their future & past events. We can potentially link to the #637 screen

Still needs a bit of thinking:

• This will only work when we add an (optional) reference from registration to user to save the user on a registration, otherwise all we have to link is a name and/or email.

• We could consider only using the email address of the user to link, or perhaps backfill the user column if we can find a user in the database with the same email as a registration

• Introducing the link adds denormalized data: we save the name and email on a registration, but if we have the user link, their name/email are saved on there as well. So we could:

  • not care (fine for me, we consider name & email to be unchangeable anyway)
  • add some callbacks to update the registration name/email when the user name/email changes (iffy)
  • always delegate name/email of the linked user when present, otherwise, fall back on the name/email fields (ok for in the app, but database-wise we'd still need the callbacks from the previous step to make sure they keep in sync)