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