Add attachments to telemetry (#2025)

Co-authored-by: Chris Mullins <[email protected]>

Author: garypretty

Diff for: libraries/botbuilder-core/src/telemetryConstants.ts

@@ -15,4 +15,5 @@ export class TelemetryConstants {
     public readonly textProperty: string = 'text';
     public readonly speakProperty: string = 'speak';
     public readonly userIdProperty: string = 'userId';
+    public readonly attachmentsProperty: string = 'attachments';
 }

Diff for: libraries/botbuilder-core/src/telemetryLoggerMiddleware.ts

@@ -247,6 +247,10 @@ export class TelemetryLoggerMiddleware implements Middleware {
             if (activity.speak && activity.speak.trim()) {
                 properties[this.telemetryConstants.speakProperty] = activity.speak;
             }
+
+            if (activity.attachments && activity.attachments.length > 0) {
+                properties[this.telemetryConstants.attachmentsProperty] = JSON.stringify(activity.attachments);
+            }
         }
 
         // Additional Properties can override "stock" properties.