By controlling the features using evironment variables we can easily
change which features are enabled in the production environment without
making changes to the application code.

If a guest's suplied identification is considered invalid by a sponsor they now have the ablility to reject them.
When a guest is rejected they will be set to unregistered and they will receive an email with a new registration link where they can correct their mistake.

When a sponsor now looks at a guest's data the phone number is in a form with the ability to edit it.
Add ability for guests to change their mobile phone number.
When a guest views their phone number, it is in a form with the ability to edit it.

Filtering is toggleable through a checkbox.

The users did not understand what to do when shown the default error
report box telling them that their information was already registered.
This commit shows a less "scary" box with less text, telling them what
to do in addition to what the problem is. Hopefully that helps.

This can be removed in the future when the backend design allows us to
save this information so that the hosts can make a decision for these
cases.

Resolves: GREG-324

Improve the tests.

When a sponsor creates a new guest invitation, and when a guest corrects their name
they must now use transcribed characters.

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

Instead of manually putting together the phone number and hoping we get
it right, we instead format the number using the phonenumbers library.
This library is already in use for validation, making it the obvious
choice. This means that the backend will only receive E.164 formatted
phonenumbers from now on. In addition, we now ensure that the number is
in fact a mobile phone number.