[AC-1705] Update PayPal Verification URL to point to updated domain

[cyprain-okeke]

Type of change

- [X] Bug fix
- [ ] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [ ] Build/deploy pipeline (DevOps)
- [ ] Other

Objective

PayPal updated its IPN verification callback URL to include a subdomain https://ipnpb.sandbox.paypal.com/cgi-bin/webscr (for Sandbox IPNs) and https://ipnpb.paypal.com/cgi-bin/webscr (for live IPNs)

Code changes

• PayPalIpnClient.cs: change the Production and sandbox url to match what is available on paypal documentation and also include User-Agent to the request header

Before you submit

• Please check for formatting errors (dotnet format --verify-no-changes) (required)
• If making database changes - make sure you also update Entity Framework queries and/or migrations
• Please add unit tests where it makes sense to do so (encouraged but not required)
• If this change requires a documentation update - notify the documentation team
• If this change has particular deployment requirements - notify the DevOps team

[bitwarden-bot]

Checkmarx One – Scan Summary & Details – cfc8025a-ec19-409b-a915-a0c8b54e870f

New Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Log_Forging	/src/Billing/Controllers/PayPalController.cs: 64	Attack Vector
	Log_Forging	/src/Billing/Controllers/PayPalController.cs: 64	Attack Vector

[Hinton]

URLs are valid per https://developer.paypal.com/api/nvp-soap/ipn/IPNImplementation/.

[cturnbull-bitwarden]

Thanks for adding logging! If you wouldn't mind, please update to include some descriptive messages in the logs. I left some comments with my suggestions, but ultimately it's up to you

[cturnbull-bitwarden]

Thank you sir!