Disallow certain characters in first and last name on creation of invitation and creation of guest

See merge request !410

Improve the tests.

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

Try to make the sponsor verify the guest correctly

See merge request !406

Install postgresql-client-15

See merge request !409

Show role comments in admin site

See merge request !408

Make role-list and role-detail return comments

See merge request !407

Add check for if email exists in guest registration

See merge request !402

GREG-341: Add access to edit comment and contact person

See merge request !399

Format phone number correctly before submitting

See merge request !405

- 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.

Role end notifier insight

See merge request !404

# Conflicts:
#   gregsite/settings/base.py

Exclude certain ous from notifications

See merge request !403

Also changed the name of some variables to make the code more readable