enableHttpCorrelationHeaders property is added to the Diagnostic entity (#4248)

Author: promoisha

specification/apimanagement/resource-manager/Microsoft.ApiManagement/preview/2018-06-01-preview/apimdiagnostics.json

@@ -485,6 +485,10 @@
         "backend": {
           "$ref": "#/definitions/PipelineDiagnosticSettings",
           "description": "Diagnostic settings for incoming/outcoming HTTP messages to the Backend"
+        },
+        "enableHttpCorrelationHeaders": {
+          "type": "boolean",
+          "description": "Whether to process Correlation Headers coming to Api Management Service. Only applicable to Application Insights diagnostics. Default is true."
         }
       },
       "required": [