Fix recursion error events models

Closes #1018 and #1015

See merge request !1511

Merge branch '1008-show-deregistration-disclaimer-text-even-if-not-registered-for-event' into 'master'

Resolve "Show deregistration disclaimer text even if not registered for event"

Closes #1008

See merge request !1506

Update dependency sphinx to v2.4.3

See merge request !1510

Resolve "/api/v1/token-auth does not return json on login failure"

Closes #975

See merge request !1492

Resolve "Missing translations in statistics page"

Closes #981

See merge request !1503

Merge branch '980-thalia-pay-process-button-enabled-in-payments-widget-even-though-tpay_enabled-false' into 'master'

Disable payment button for Thalia Pay in payment widget

Closes #980

See merge request !1501

Update dependency freezegun to v0.3.15

See merge request !1495

Fixed login message visible

Closes #968

See merge request !1500

Luc Knol authored Feb 19, 2020 and Sébastiaan Versteeg committed Feb 19, 2020

Removed login button and added message "No registration required" for events for which registration is not required.

Added a banner for members who are banned from certain or all events.

Closes #987

See merge request !1494

Marthijn van den Nieuwenhuizen authored Feb 19, 2020 and Sébastiaan Versteeg committed Feb 19, 2020

Added banner for people banned from certain events

Added a banner for people who are banned from certain events.

Update dependency bleach to v3.1.1

See merge request !1498

Update dependency sphinx to v2.4.2

See merge request !1490

Resolve "Event admin view does not include 'user-tools' like other admin templates"

Closes #978

See merge request !1483

Set Postgres Password in CI

See merge request !1497

Add base class for all payable objects

Closes #1010

See merge request !1493

Update dependency sphinx to v2.4.0

See merge request !1489

Create dependencies Docker image

See merge request !1488

Don't build Docker image using docker-compose

See merge request !1487

Add push notifications for newsletters

Closes #922

See merge request !1426

Success_messages added for every exam and summary upload

Closes #998

See merge request !1482

Resolve "No favicon for the admin site"

Closes #999

See merge request !1481