cherrypy: fix handling of raw application/x-www-form-urlencoded traffic

[nicholasmhughes]

What does this PR do?

handle the preservation of raw application/x-www-form-urlencoded traffic in cherrypy

What issues does this PR fix or reference?

N/A

Previous Behavior

cherrypy natively parsed the incoming x-www-form-urlencoded traffic into a dictionary, which was then put into the post key when the event fired. the raw_body was manually set to an empty string, because cherrypy will leave raw_body as None when parsing x-www-form-urlencoded traffic. therefore, the body key of the event was always an empty string in the case of x-www-form-urlencoded traffic, where that key would normally contain the raw request when processing other types of traffic.

I consider this "broken" because it doesn't provide a way to handle the raw data at all when parsing x-www-form-urlencoded traffic. This functionality is required when attempting to validate Slack webhooks since the raw x-www-form-urlencoded string is hashed for a signature and cannot be deserialized because it will destroy the order of the parameters and provide no mechanism to validate the traffic.

New Behavior

instead of using the native cherrypy parsing, which throws away the raw request when creating the params dictionary, we read the raw data into a string (which ends up in the body key in the event) and then perform manual parsing of the tokens into a dictionary using parse_qsl to set the contents of the post key in the event. since the post key output functionality isn't changed and the body key was always empty and therefore wasn't relied on, this is a low impact change.

Tests written?

Yes

Commits signed with GPG?

Yes

[nicholasmhughes]

@dwoz added test and all tests passing

[nicholasmhughes]

@dwoz @sagetherage assuming these tests pass (I'm going to bed), can this PR get some love? I think we're coming up on 11 months from the original PR date and I keep having to track to new formats and tests.