feat(invitation)!: rename to guest

[dargmuesli]

The invitation table currently hold information about an event's guest / attendee instead of detailed data about an invitation, e.g. send timestamps and so on. Thus, the currently invitation table should be renamed to guest to make room for a proper invitation table. This is a breaking change of course.

A new invitation table can then be created for this tasks:

• feat(invitation): track send events #10

The current invitation table / would be guest table can be extended as defined in the following tasks:

• feat(guest): add reason to feedback #20
• feat(guest): allow to add multiple at once #74