[Error Boundary] Add stack trace to error payload to aid in troubleshooting rendering errors (#3032)

## Summary:
The current Rendering Errors dashboard displays an error message, but nothing about where the error occurred. This PR adds the error stack to the error object sent to the dashboard service.

Issue: LEMS-3714

## Test plan:
1. Deploy to PROD
1. Wait a day or two to start receiving the data
1. Update dashboard to use the new data

**OR**

1. Run the updated unit test for the `widget-container.tsx`

Author: mark-fitzgerald

Reviewers: catandthemachines

Required Reviewers:

Approved By: catandthemachines

Checks: ⏭️  1 check has been skipped, ✅ 10 checks were successful

Pull Request URL: #3032

Author: mark-fitzgerald

.changeset/beige-spiders-knock.md

@@ -0,0 +1,6 @@
+---
+"@khanacademy/perseus-core": minor
+"@khanacademy/perseus": patch
+---
+
+[Error Boundary] Add stack trace to error payload to aid in troubleshooting rendering errors

packages/perseus-core/src/analytics.ts

@@ -23,6 +23,7 @@ export type PerseusAnalyticsEvent =
               widgetType: string;
               widgetId: string;
               message: string;
+              stack: string | undefined;
               userAgent: string;
           };
       }

packages/perseus/src/__tests__/widget-container.test.tsx

@@ -123,15 +123,35 @@ describe("widget-container", () => {
         );
 
         // Assert
-        expect(onAnalyticsEventSpy).toHaveBeenCalledWith({
+        const expectedPayload = {
+            widgetSubType: "null",
+            widgetType: "mock-widget",
+            widgetId: "mock-widget 1",
+            message: "MockWidget failed to render",
+            stack: "Error: MockWidget failed to render\n    at MockWidgetComponent",
+            userAgent: "userAgent",
+        };
+        const expectedEventInfo = {
             type: "perseus:widget-rendering-error:ti",
-            payload: {
-                widgetSubType: "null",
-                widgetType: "mock-widget",
-                widgetId: "mock-widget 1",
-                message: "MockWidget failed to render",
-                userAgent: "userAgent",
-            },
-        });
+            payload: expectedPayload,
+        };
+        expect(onAnalyticsEventSpy).toHaveBeenCalledTimes(1);
+        // NOTE: We do a partial match on the stack trace since it may vary across
+        // environments/runs.
+        const analyticsEventArgument = onAnalyticsEventSpy.mock.calls[0][0];
+        expect(Object.keys(analyticsEventArgument)).toEqual(
+            Object.keys(expectedEventInfo),
+        );
+        expect(analyticsEventArgument.type).toEqual(expectedEventInfo.type);
+        expect(Object.keys(analyticsEventArgument.payload)).toEqual(
+            Object.keys(expectedPayload),
+        );
+        // Checking that only the beginning of the stack trace matches so that
+        // running this locally won't fail. Plus, the stack trace is frickin' long!
+        expect(
+            analyticsEventArgument.payload.stack.startsWith(
+                expectedPayload.stack,
+            ),
+        ).toEqual(true);
     });
 });

packages/perseus/src/widget-container.tsx

@@ -176,6 +176,7 @@ class WidgetContainer extends React.Component<Props, State> {
                                         widgetType: type,
                                         widgetId: this.props.id,
                                         message: error.message,
+                                        stack: error.stack,
                                         userAgent: userAgent,
                                     },
                                 });