Engagement Dashboard - "Exceeded memory limit for $group" error

Description:

"Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse" error is triggered when opening "Channels" panel inside Engagement Dashboard.

Steps to reproduce:

1. Go to Engagement Dashboard
2. Select "Channels" panel, error will be triggered"

Server Setup Information:

• Version of Rocket.Chat Server: 3.3.0-rc.2

• API call which triggers the error

/api/v1/engagement-dashboard/channels/list?start=2020-05-18T03:00:00.000Z&end=2020-05-25T02:59:59.999Z&offset=0&count=25

Relevant logs:

• Console logs
  Failed to load resource: the server responded with a status of 400 () /client/hooks/useEndpointData.js:1 Error at originalCallback (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:418) at Object.processTwoFactorError (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:418) at Object.a [as error] (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:418) at c (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:48) at Object.fireWith [as rejectWith] (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:48) at w (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:48) at XMLHttpRequest.<anonymous> (4220d2ec2b635785e8eb297660d4942b3e8e9abe.js?meteor_js_resource=true:48)

Start by tracing the /api/v1/engagement-dashboard/channels/list endpoint from the Channels panel and compare it with the client error shown from useEndpointData.js. Reproduce the request with the supplied date range, offset, and count, then identify why the aggregation exceeds the memory limit. Done means the Channels panel loads successfully without the reported error.