GREG-60: Adding some feedback to user when he presses submit

See merge request !90

Adding some e-mail validation tests

See merge request !91

Add invitations

See merge request !85

- Introduces the Invitation and InvitationLink models for keeping track
  of guest invitations and the links connected to them.
- Adds a post endpoint accessible by sponsors to create invitations for
  guests.
- Adds a get endpoint for the guests to review their invitation
  information.
- Adds a post endpoint for the guests to confirm their invitation with
  updated mobile_phone number if they want.
- Removes token field from Person since it is not used.

GREG-60: Adding a utility method for validation national ID numbers

See merge request !86

GREG-60: Validate e-mail

See merge request !88

Fix formatting to comply with linting rules

See merge request !89

Issue: GREG-42

Greg 42 email

See merge request !83

Issue: GREG-42

Issue: GREG-42

GREG-60: Updating which fields are requried

See merge request !87

GREG-60: Mobile phone validation

See merge request !81

Greg 51 deploy frontend

See merge request !84

Make all URLs relative. Move /oidc and /admin endpoints up from /api and proxy them during development.

Add a Containerfile for the frontend. Allow configuration to be injected. Move static files directory for Django.

GREG-60: Update wizard fields

See merge request !80

Just print mails to console instead so no one sends real emails on accident

Issue: GREG-42

Issue: GREG-42

Issue: GREG-42

Issue: GREG-42