[Security] Bump django from 2.1.11 to 2.2.7

[dependabot-preview]

Bumps django from 2.1.11 to 2.2.7.

Commits

• 27f2b44 [2.2.x] Bumped version for 2.2.7 release.
• 1cbf607 [2.2.x] Updated man page for Django 2.2.
• 6f26693 [2.2.x] Added release dates for 2.2.7, 2.1.14, and 1.11.26.
• 785d170 [2.2.x] Fixed #30931 -- Restored ability to override Model.get_FIELD_display().
• eb8a53c [2.2.x] Fixed typo in docs/ref/signals.txt.
• 3ca4457 [2.2.x] Corrected error message in Many-to-many relationships docs.
• 972eef6 [2.2.x] Fixed #30927 -- Simplified an example of test for the deprecation war...
• 9d15f1e [2.2.x] Fixed #30917 -- Clarified formsets topic documentation.
• 4cc1549 [2.2.x] Fixed #13750 -- Clarified need to reopen models.ImageField.image file...
• 4d992bc [2.2.x] Fixed typo in docs/topics/files.txt.
• Additional commits viewable in compare view

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[dependabot-preview]

We've just been alerted that this update fixes a security vulnerability:

Sourced from The GitHub Security Advisory Database.

Moderate severity vulnerability that affects django
Django 2.1 before 2.1.15 and 2.2 before 2.2.8 allows unintended model editing. A Django model admin displaying inline related models, where the user has view-only permissions to a parent model but edit permissions to the inline model, would be presented with an editing UI, allowing POST requests, for updating the inline model. Directly editing the view-only parent model was not possible, but the parent model's save() method was called, triggering potential side effects, and causing pre and post-save signal handlers to be invoked. (To resolve this, the Django admin is adjusted to require edit permissions on the parent model in order for inline models to be editable.)

Affected versions: [">= 2.1.0, < 2.1.15"]

[dependabot-preview]

Superseded by #184.