[Bug 1125536] Convert all rate limiting to a standard helper.

[mythmon]

This converts all the rate limiting we have to use two related functions kitsune.sumo.decorators.ratelimit and kitsune.sumo.utils.is_ratelimited. These work largely like their django-ratelimit versions, and in-fact use django-ratelimit themselves, except they are simplified and specialized to our needs. In particular, they respect a permission for bypassing rate limits, so we can have a global switch for this, and they all log when a user is over the rate limit.

The rate limit overages are recorded in kitsune.journal.models.Record, which is loosely based off fjord.journal.models.Record, which @willkg wrote. I modified it a lot, since I don't think we needed everything Fjord needed.

This isn't done yet

• Make new ratelimit decorator.
• Make new is_ratelimited function.
• Add "logging".
• Add the permission some how (I think this will be useful).
• Test the permissions
• Test the logging

f?

[mythmon]

All the boxes above are checked. I think this is ready to go. r?

[rlr]

but that test fails. gah!

[rlr]

yay! so much cleaner

[mythmon]

Oops, I forgot to git add the migration that creates the permission. That is why the test failed.

[mythmon]

🎆

[rlr]

yay 💥