[DEV] Customer Payments

[maxceem]

This functionality was implemented as per challenge https://www.topcoder.com/challenges/25fa2d11-9f69-4d81-9f67-fb2eb15cec6a?tab=details.

See the guide https://github.com/topcoder-platform/tc-project-service/tree/feature/customer-payments/docs/guides/customer-payments and demo video.

Deployment guide

1. Create ElasticSearch index customer_payments and customer_payments_test
2. Set env variable STRIPE_SECRET_KEY
3. Run SQL migration directly to AWS DB https://github.com/topcoder-platform/tc-project-service/blob/a37d49b45bb6a54c18c956541a3e61a41cc6cf2d/migrations/20212801_customer_payment.sql
4. config Topcoder's Gateway to forward /v5/customer-payments URLs to the Project Service's URL /customer-payments
5. Merge Project ES Processor PR [DEV] Support for Customer Payments project-processor-es#71
6. Merge this PR