Messages Posted through API calls don't reflect on the sender's end

Description:

When a user sends a message through an API call, the receiver receives and sees the message but the sender doesn't see anything. It's like no communication took place from the senders perspective.

Steps to reproduce:

1. Setup Rest API configuration,
2. Follow the format according to the docs (here)[https://docs.rocket.chat/api/rest-api/methods/chat/postmessage] to post a message
3. You should have something like this:

Endpoint - http://localhost:3000/api/v1/chat.postMessage?
-----
"channel": "@theUserToSend"
"text": "Message to send"

4. Then make the post request

Expected behavior:

Expected to see that a message has been posted from me to them but I don't see anything.

Actual behavior:

No sign of any sent Message

But the receiver sees my message

Server Setup Information:

• Version of Rocket.Chat Server: 3.12.0-develop
• Operating System: Ubuntu
• Deployment Method: web
• Number of Running Instances: 1
• DB Replicaset Oplog:
• NodeJS Version: 12.18.4
• MongoDB Version:4.2.8

Start by reproducing the issue with the documented chat.postMessage REST endpoint and compare the sender and receiver views. Trace the API message-posting flow and its sender-side update behavior; done means a message posted through the endpoint appears for both sender and receiver.