Keep the entrypoint UUID out of webhooker's own logs (closes #531)

On the receiver route the access log and the per-entrypoint 429 line
name the route pattern whatever the status. The received line names
the entrypoint and webhook IDs, and the unknown-entrypoint line logs
no path. The pattern is middleware.ReceiverRoute, which routes.go
registers the receiver with.

The README says the proxy's access log holds the UUID and must be
protected like the URL, and its access-log, rate-limit, Sentry and
log-size passages now match the code.

Model: opus-5-5

internal/handlers/webhook.go

@@ -10,7 +10,6 @@ import (
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
-	"sneak.berlin/go/webhooker/internal/logfield"
 	"sneak.berlin/go/webhooker/internal/middleware"
 )
 
@@ -49,14 +48,13 @@ func (h *Handlers) HandleWebhook() http.HandlerFunc {
 			return
 		}
 
-		// Logged only once the UUID is known to name a real
-		// entrypoint. The UUID comes straight out of the path on
-		// the one unauthenticated endpoint, so logging it before
-		// the lookup let a client write an INFO line per invented
-		// path; the request itself is already in the access log
-		// and a miss is already logged at DEBUG.
+		// Logged only once the lookup has found the entrypoint, so
+		// an invented path writes no INFO line; a miss is logged at
+		// DEBUG. The entrypoint is named by its ID: the UUID is its
+		// credential and is never logged.
 		h.log.Info("webhook request received",
-			"entrypoint_uuid", entrypointUUID,
+			"entrypoint_id", entrypoint.ID,
+			"webhook_id", entrypoint.WebhookID,
 			"method", r.Method,
 			"remoteIP", middleware.RemoteIP(r),
 			"clientIP", middleware.ClientIP(r),
@@ -133,17 +131,10 @@ func (h *Handlers) lookupEntrypoint(
 		"path = ?", entrypointUUID,
 	).First(&entrypoint)
 	if result.Error != nil {
-		// The receiver is unauthenticated and /h/{uuid}
-		// matches any single segment, so this value is entirely
-		// client-chosen on exactly the branch where the lookup
-		// failed. DEBUG is off by default; the cap is what keeps
-		// turning it on from restoring an unbounded write.
-		h.log.Debug(
-			"entrypoint not found",
-			"path", logfield.Truncate(
-				entrypointUUID, logfield.MaxBytes,
-			),
-		)
+		// Not even an unknown UUID is logged. The receiver's log
+		// lines never carry the path segment, which is a credential
+		// whenever it names an entrypoint.
+		h.log.Debug("entrypoint not found")
 		http.NotFound(w, r)
 
 		return entrypoint, false