Donation confirmation pages for analytics

For GiveCampus integrations and API.

Standard giving confirmation/post-payment pages are per-contribution routes: /campaigns/<project>/donations/<contribution>. There is no single fixed school confirmation URL. Access is authorized for that gift, and a configured post-payment redirect can change the final destination. Verify the actual successful flow when setting an analytics trigger; exclude entry /new pages, failures and repeat visits, and do not treat a pageview as proof of a unique settled payment. Do not place private gift URLs in public documentation.