Add new django tutorial

[glasnt]

Description

Implements new Django tutorial with integration testing. (Internal cl/309679445)

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.6 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• Please merge this PR for me once it is approved.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample

[grant]

Thanks for the PR.

Is there any more background to this sample? Will it be included under cloud.google.com/run? If not, maybe we can host the sample in a community tutorial folder with our other cloud run tutorials.

Is the tutorial original? I didn't review the code as it doesn't seem to be originally authored.

CC @grayside

[grant]

Are we 100% sure that Google authored this code and we're able to claim it under this repo's license? It seems like this tutorial should be hosted on Django's website/repo and not here.

[glasnt]

I followed the pattern from the kubernetes and appengine samples.

[glasnt]

Linting was failing since typechecks are currently configured to include typechecking noxfile.py itself, which is copied per workspace from ~/noxfile-template.py.

"⚠️" marked edits attempt to correct this by adding typechecks to noxfile-template.py itself, rather than adding noxfile.py to the ignore list.

Happy to cherrypick these comments to a different branch and rebase this branch, for code cleanliness. (This branch also needs a squash, maybe, not seeing anything in AUTHORING_GUIDE about such things.

[averikitsch]

lgtm pending test passing

[leahecole]

Super minor changes! Ping me when you're ready for what is most likely the final review