update the externalname configuration for aws_lambda_alias to reflect…

[djeremiah]

… the true ID format

Description of your changes

This PR changes the ExternalName configuration for aws_lambda_alias to match the id format expected by terraform. Specifically, the config was previously based on the import syntax for the resource, but TF uses the full ARN as the Id.

Fixes #653

I have:

• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Local testing - provisioned a lambda function via S3 bucket and a function alias for a published version.

[jeanduplessis]

/test-examples="examples/lambda/alias.yaml"

[jeanduplessis]

@djeremiah We have uptest failing on the current example in examples/lambda/alias.yaml – could you have a look to see if the example needs updating so we can ensure we keep e2e coverage for this resource.

[djeremiah]

Do we generally want a single file to provide the e2e test? Or can we include other examples as dependencies? Testing the Alias will require publishing a lambda function. The plumbing for all of that appears to be fully included in examples/function.yaml, so we can either re-run the test including that example, or we can copy the needed items into alias.yaml.

[jeanduplessis]

We tend to want to include all the necessary elements in the example file so that they can be run independently.

[djeremiah]

/test-examples="examples/lambda/alias.yaml"

[djeremiah]

/test-examples="examples/lambda/alias.yaml"

[sergenyalcin]

Thanks @djeremiah LGTM! I also tested and validated this PR in my local setup.