feat(transform): Add Send for AWS Lambda

[jshlbrd]

Description

• Adds a send_aws_lambda transform
• Adds an example of using the new transform to continuously retry a failed S3 trigger

Motivation and Context

This resolves #57 with an emphasis on adding as little new code as possible. It's mostly trivial to build a retry pipeline using existing Substation components. You can test the new example by running this and then uploading a file to the created S3 bucket:

make check
make build-aws
make deploy-aws DEPLOYMENT_DIR=examples/terraform/aws/s3/retry_on_failure AWS_APPCONFIG_ENV=example

How Has This Been Tested?

End-to-end tested using the added example.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[shellcromancer]

Looks good, verified that this implementation meets the needs of an external user as well. 👍

[shellcromancer]

Style: without string formatting or error wrapping we could use errors.New here

[jshlbrd]

Since every error gets wrapped in a string to identify the transform (e.g. fmt.Errorf("transform: send_aws_lambda: %v", err)), I'm going to leave this as-is for now for readability consistency.