telemetry: add tracing

- telemetry/tace: add traces throughout code
- telemetry/metrics: nest metrics and trace under telemetry
- telemetry/tace: add service name span to HTTPMetricsHandler.
- telemetry/metrics: removed chain dependency middleware_tests.
- telemetry/metrics: wrap and encapsulate variatic view registration.
- telemetry/tace: add jaeger support for tracing.
- cmd/pomerium: move `parseOptions` to internal/config.
- cmd/pomerium: offload server handling to httputil and sub pkgs.
- httputil: standardize creation/shutdown of http listeners.
- httputil: prefer curve X25519 to P256 when negotiating TLS.
- fileutil: use standardized Getw

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/httputil/errors.go

@@ -23,21 +23,11 @@ func (h Error) Error() string {
 	return fmt.Sprintf("%d %s: %s", h.Code, http.StatusText(h.Code), h.Message)
 }
 
-// CodeForError maps an error type and returns a corresponding http.Status
-func CodeForError(err error) int {
-	switch err {
-	case ErrTokenRevoked:
-		return http.StatusUnauthorized
-	}
-	return http.StatusInternalServerError
-}
-
 // ErrorResponse renders an error page for errors given a message and a status code.
 // If no message is passed, defaults to the text of the status code.
 func ErrorResponse(rw http.ResponseWriter, r *http.Request, e *Error) {
-	requestID := ""
-	id, ok := log.IDFromRequest(r)
-	if ok {
+	var requestID string
+	if id, ok := log.IDFromRequest(r); ok {
 		requestID = id
 	}
 	if r.Header.Get("Accept") == "application/json" {