Filtering is toggleable through a checkbox.

- Add link to clearify why it's important
- Change name of button and header in pop-up

Calling norwegian fnr "National ID number" makes people input their id
numbers from their home country in addition to their passport numbers.

This text change hopefully makes it clearer for our non-norwegian
friends.

Sponsosr can now click a button next to passport/fnr values on the
guest info page to see the source and verifier of the value.

Resolves: GREG-275

By moving the notifications to midnight on the day they expire we
simplify the work of systems integrating with greg. The frontend has
also been updated to say that end dates are "to (including)" to clarify
that the roles are valid on their last day.

Resolves: GREG-2688

Introduces the invalid field on the Identity model. The field is used to
indicate that the Identity is in invalid. This is useful when a value is
not a working value, even though the value passes validation checks,
like unused national id numbers, emails tied to non-existing domains,
etc.

Resolves: GREG-252

Issue: GREG-237

Issue: GREG-237

Relabel the invitation resend button to make its purpose more clear.

Adding a role without selecting either of these makes no sense, and will
be refused by the backend accordingly.

Displays a warning if the identifier the sponsor wants to verify is
already assigned to someone in the IGA, or if the backend could not
contact the IGA to check.

It turns out that different institutions have different criteria for
what counts as good enough papers to verify an Norwegian National
identity number. This commit makes it possible to specify different text
for each language option for each instance.

Resolves: GREG-199

Resolves: GREG-167

Resolves: GREG-177