Use DRF's get_object_or_404 instead of the default in the pizzas viewset

See merge request !628

added a category field and added it to the admin with filtering

Closes #537

See merge request !634

Add backwards compatible avatar object to events and members API for better thumbnails

Closes #527

See merge request !636

Merge branch '516-als-admin-is-de-tijd-die-in-het-evenementenoverzicht-staat-hetzelfde-als-de-tijd-die-staat-ingesteld-bij-het-evenement' into 'master'

Made the start date a naive when being sent to the admin overview page.

Closes #516

See merge request !626

Use get for dict access in order serializer

See merge request !629

Add start and end query parameters to events API

Closes #547

See merge request !623

Fix documents page font

See merge request !624

Hide association documents when unavailable

Closes #535

See merge request !625

Implement exception filter

Closes #534

See merge request !622

Hides HTTP Cookies and Authorization header

Replace pizzas json view by API usage

Closes #531

See merge request !615

Merge branch '513-almost-adjacent-committee-memberships-should-keep-member-since-date' into 'master'

Combine almost-adjacent committee memberships on committee page

Closes #513

See merge request !621

Registrations feature

See merge request !533

Move members welcome email to emails.py

Remove BecomeAMemberDocument model

Add registrations app with models

Add emails.py and email templates

Model changes:
- Remove email_confirmed boolean from Registration model
- Change default value of Registration model status to 'confirm'
- Make Registration model email unique

Add first model tests for Registration

Write clean() for Registration

Fix PEP8 errors

Add init file to tests directory

Make Membership types constants instead of using the string value everywhere

Change membership lengths to constants in Entry model

Mention upgrade behaviour in registrations README

Use constants in registrations models test

Use constants for Entry status and fix membership_type argument in models test

Convert payment types to constants

Override translation language in registration emails by preferred language

Add services.py and tests

Implemented services.py

Add admin.py, fix docs in services.py and add app to sphinx

Wrote email contents

Make Registration email not unique

Fix call to renewal complete email in services.py

Add mail outbox assert to test_process_payment

Fix email formatting and do not completely block payment permissions

Make welcome mail non-trimmed

Change model admin changeform and add accept/reject buttons for registration and renewal

Add process buttons to payment admin and add permissions for reviewing and processing

Make some changes to the registrations admin (RenewalAdmin now inherits from RegistrationsAdmin) and add some tests

Add confirmation messages to custom admin calls, and redirect back to change form

Improve automatic username generation

Prevent processing payment for member with already active study membership

Rewrite registrations views to classes

Add tests for views

Fix sending confirmation email and related tests

Send confirmation mail after registration creation

Change README to reflect new supposed behaviour

Add frontend views

Update migration file to reflect model changes

Update view tests to reflect url changes

Add tests for forms

Change birthday field to SelectDateWidget

Generate username when accepting registration, not when processing payment

Change README to reflect new rules

Improve renewal admin

Move programme and starting year checks to model

Rename views and form to be member only

Make changes to model

Fix typo's and price for renewal

Fix tests

Move renewal validation to model instead of form

Change rules for processing in August

Update migration

Make renewal member field not readonly for new obj

Fix lecture year in test

Add confirmation to accept/reject buttons

Add localization for registrations

Change until date for new memberships to 01-09

Add processing date to payments

Add updated_at field to Entry model

Creation of renewal determines price

Fix tests

Always start membership renewals in August in September

Add board notifications

Move become a member page to registrations app

Update localisation

Add link to registration renewal on account page

Change file names and add link to documents page

Add language field to Device model and make verbose names lowercase

See merge request !620

Fix creating orders for other users using the pizza API

See merge request !605

Fix push notifications admin search

Closes #540

See merge request !619

Use more specific exceptions and include context

See merge request !618

Fix MemberMiddleware in the API

See merge request !616

The MemberMiddleware was broken when DRF's TokenAuthentication was used.

Remove bare except clauses

See merge request !617

A new check in flake8 complains about them.

Grayscale inaccessible albums

Closes #166

See merge request !614