Request parameters and headers to change the behaviour of the 429 Too Many Requests response.

[jimbojim1997]

This PR adds two request parameters and headers which change the value of the response header Retry-After of the 429: Too Many Requests response.

Parameter seconds / header X-Retry-After-Seconds

• Sets the number of seconds used for the Retry-After response header.
• Default: 5 seconds (same as existing implementation).

Parameter format / header X-Retry-After-Format:

• Sets the format of the Retry-After resonse header.
• Accepted values:
  • Any value returns a number of seconds
  • date returns the current time + seconds in the HTTP Date format.
• Default: seconds format (same as existing implementation).

Also includes tests and additional information on the home page detailing these parameters.

[aaronpowell]

Finally getting to do a cleanup on the repo, and looking at this PR, I think it does much more than is really desired, I think it'd be a lot simpler if I just added a way to provide a custom response header value, and then from the caller you can specify that in the request and it just returns what you requested.