Refactor `apigw.tf` - export lambdas to module

[eranelbaz]

For each lambda, we need (at least)

• aws_api_gateway_integration
• aws_api_gateway_integration_response
• aws_api_gateway_method
• aws_api_gateway_resource

This makes the apigw.tf file very long, and each change require us to repeat ourself a lot

Maybe we can export all of those to modules or use existing open source lambda module