Proxying API Gateway Lambdas

manage-frontend has a standardised mechanism for proxying API Gateway frontend Lambdas from guardian/support-service-lambdas, notably...

• holiday-stop-api
• delivery-records-api
• cancellation-sf-cases-api

In summary, it uses CloudFormation and APIGateway clients of the aws-sdk to 'discover' the API gateway hostnames and API keys by name, rather than having to maintain that config in S3 or ParameterStore (see https://github.com/guardian/manage-frontend/pull/351).

As with all AJAX calls made by the client, we proxy services (see wiki/Server-side-Proxying for general rationale), and in this case...

• using the retrieved hostname and API keys (see above)

• adds the x-identity-id header using the value which came from IDAPI (see wiki/IDAPI-Integration)

• selects the right STAGE instance of the API Gateway Lambda, based on whether the user is a test-user

  Stage of manage-frontend	normal mode	test user mode
  DEV (local machine)	DEV Lambda* (DEV SF/Zuora)	CODE Lambda (UAT SF/Zuora)
  CODE	DEV Lambda* (DEV SF/Zuora)	CODE Lambda (UAT SF/Zuora)
  PROD	PROD Lambda (DEV SF/Zuora)	CODE Lambda (UAT SF/Zuora)

  * Yes indeed there is a DEV Stack for the lambda, which is available in riff-raff as of guardian/prism/pull/75