Add debug.ping endpoint

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server/schema/services/debug.conf

@@ -0,0 +1,16 @@
+_description: "debugging utilities"
+ping {
+    authorize: false
+    "2.9" {
+        description: "Ping server"
+        request {
+            type: object
+            additionalProperties: true
+        }
+        response {
+            type: object
+            properties: {
+            }
+        }
+    }
+}