Added resolve_customer lambda handler

[schaefi]

The resolve_customer handler expects an event providing the x-amzn-marketplace-token. It will then resolve customer information from the metering marketplace as well as the entitlements for this customer's ID and product code. The return type API is documented in the header of the lambda_handler entrypoint

[schaefi]

ok problem with this code is that I implemented it according to the AWS documentation. I was not able to test this code for real because that requires me to have a proper x-amzn-marketplace-token which I don't have and which is the result of a click on the subscription vendor button.

[schaefi]

It's expected that the resolve_customer lambda is triggered by an AWS API Gateway. This information should be added to the code and the code also needs to change because the event structure is not correctly read by the PR for this trigger mechanics. Here is an example event source

[INFO]	2025-01-15T16:44:01.777Z	1c84a83d-f813-4e1a-bacc-c42ab75ebf7d	EVENT: {'version': '2.0', 'routeKey': 'ANY /ms-lambda-from-container', 'rawPath': '/default/ms-lambda-from-container', 'rawQueryString': '', 'headers': {'accept': '*/*', 'content-length': '31', 'content-type': 'application/x-www-form-urlencoded', 'host': 'jfh2r389u9.execute-api.eu-central-1.amazonaws.com', 'user-agent': 'curl/8.0.1', 'x-amzn-trace-id': 'Root=1-6787e5d1-5850b9f64c02c6df0926b405', 'x-forwarded-for': '79.201.150.192', 'x-forwarded-port': '443', 'x-forwarded-proto': 'https'}, 'requestContext': {'accountId': '810320120389', 'apiId': 'jfh2r389u9', 'domainName': 'jfh2r389u9.execute-api.eu-central-1.amazonaws.com', 'domainPrefix': 'jfh2r389u9', 'http': {'method': 'POST', 'path': '/default/ms-lambda-from-container', 'protocol': 'HTTP/1.1', 'sourceIp': '79.201.150.192', 'userAgent': 'curl/8.0.1'}, 'requestId': 'EcDY1h1zFiAEPLQ=', 'routeKey': 'ANY /ms-lambda-from-container', 'stage': 'default', 'time': '15/Jan/2025:16:44:01 +0000', 'timeEpoch': 1736959441730}, 'body': 'eyJuYW1lIjogIk1hcmN1cyIsICJhZ2UiOiAiNTIifQ==', 'isBase64Encoded': True}

• code must check body encoding type
• real request event data is below body key, adapt handler method accordingly
• response output must include at least: isBase64Encoded, statusCode and body, see https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-input-format for details