Update Slack File Upload Method

[Hemanthr1]

Issue Description

Implement Slack's new file upload method, as the older version is scheduled to be deprecated by May 2025.

Expected Behavior

The application should successfully upload files using Slack's updated file upload method without any issues.

Actual Behavior

Currently, the application relies on an outdated file upload method, which will no longer be supported after May 2025.

[Pavankumar07s]

Hii @Hemanthr1 I want to work on this improvement feature.

[Hemanthr1]

@Pavankumar07s Assigned. @dhairya-quash please co-ordinate with setup if needed.

[dhairya-quash]

@Pavankumar07s do reach out to me if any assistance is needed.