mod_http_oauth2: Reduce authorization code validity time to 2 minutes RFC 6749 states > A maximum authorization code lifetime of 10 minutes is RECOMMENDED. So 15 minutes was way too long. I was thinking 5 minutes at first but since this should generally be instant, I settled on 2 minutes as a large guesstimate on how slow it might be on slow links.

This module logs events where more than a certain amount of CPU time was
spent.

``` lua
log_cpu_threshold = 0.01 -- in seconds, so this is 10 milliseconds
```

Uses the Lua
[`os.clock()`](http://www.lua.org/manual/5.2/manual.html#pdf-os.clock)
function to estimate CPU usage.