** Implement to create HTTP request / response loggers.
**
** 'logIncoming()' is called once per request *before* any request processing, and 'logOutgoing()' is called *after* all processing has finished.
** Here's an example basic logger:
**
** pre>
** syntax: fantom
**
** using afIoc
** using afConcurrent
**
** const class BasicRequestLogger : RequestLogger {
** @Inject private const HttpRequest httpReq
** @Inject private const HttpResponse httpRes
** @Inject private const LocalRef startTimeRef
** @Inject private const Log log
**
** new make(|This|in) { in(this) }
**
** override Void logIncoming() {
** startTimeRef.val = Duration.now
** }
**
** override Void logOutgoing() {
** timeTaken := Duration.now.minus(startTimeRef.val).toLocale
** msg := "${httpReq.httpMethod} ${httpReq.url.encode} ${httpRes.statusCode} in ${timeTaken}"
** log.info(msg)
** }
** }
** <pre
**
** `Middleware` could be used to log HTTP requests, but 'Middleware' is wrapped in an error handling mechanism.
** So if an error handler changes response, this may not be seen by the logger.
**
** 'Requestloggers' are invoked *outside* of error handling, so the response seen by the logger IS the response sent to the browser.
** The caveat to this, is that ALL errors raised by 'RequestLoggers' are simply logged and swallowed.
** So unless you're monitoring the server logs, you're unlikely to see any logger problems.
**
**
**
** IoC Configuration
** =================
** Instances of 'RequestLogger' should be contributed to the 'RequestLoggers' service. Example:
**
** syntax: fantom
** @Contribute { serviceType=RequestLoggers# }
** Void contributeRequestLoggers(Configuration config) {
** config.add(MyRequestLogger())
** }
**
** A config key is not required, but it's polite to provide one so others may remove it, or order their loggers before or after yours.
** You can also use IoC to autobuild your logger should it have any dependencies:
**
** syntax: fantom
** @Contribute { serviceType=RequestLoggers# }
** Void contributeRequestLoggers(Configuration config) {
** config["myLogger"] = config.build(MyRequestLogger#)
** }
**
const mixin RequestLogger {
** Called *before* all request processing.
virtual Void logIncoming() { }
** Called *after* all request processing.
virtual Void logOutgoing() { }
}
