feat: Swagger docs for `/pay` endpoints #3021

Job	Run time
Check file changes	16s
E2E tests	9m 23s
Generate Hasura Change Summary	0s
Run API Tests	48s
Build React App	4m 1s
Run Integration tests	5m 12s
Run React Tests	0s
Upsert Vultr Instance	29m 32s
Run Pulumi Preview	0s
Run Healthcheck on Pizza Services	0s
	49m 12s

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