[REST API] Coupons - Make Jetpack requests available as REST API requests.

[selanthiraiyan]

Closes: #

Description

Testing instructions

Screenshots

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr8477-d1b7b55 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[peril-woocommerce]

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Generated by 🚫 dangerJS

[selanthiraiyan]

I will get back to changing the coupon remote after we stabilise the changes to the network layer. #8483