Added UPI integration with the App and setup the webhook

[Priyansh61]

Overview

1. This PR fixes or fixes part of #[fill_in_number_here].
2. This PR does the following: [Explain here what your PR does and why]

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• [ ] The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
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