chore(infra-gen2): Gen 2 infra

[Equartey]

Description of changes:
This adds a new infra-gen2 directory to hold Gen 2 backends for integration testing. It includes a script tool/deploy_gen2.dart that will:

1. Run the amplify sandbox command in each folder under /backends
2. Combine multiple backend outputs for a given category into amplifyEnvironments
3. Copy and distribute the amplify_outputs.dart to example apps
4. Create and upload the config files to respective S3 buckets for CI use
   

Additionally, this includes a bash file, pull_test_gen2_backend.sh, that lives in example apps to allow GitHub Actions to pull the required config for a given App.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[Jordan-Nelson]

Q: Which backend becomes the "default" (the one set to const amplifyConfig = ... in the outputs file? I added a new backend and that one is now the "default". Maybe it would be beneficial to specify one as default?

[Equartey]

It's currently implicit, as the first one in the list will be default. I'm not sure its work adding more logic to explicitly set the default since this script is typically used once-per team member.

[Jordan-Nelson]

Q: Do you need this since you have if (category.backends.length <= 1) continue above?

[Equartey]

Yeah, this is outside the for loop (scope of previous if statement), so single backend groups would still hit this. If it was removed, all output files would have an empty amplifyEnvironments definition, which might not be a bad thing?

[Jordan-Nelson]

Q: This will return an empty string if there is no bucket match. It will return the first bucket if there are multiple matches. Is that the desired behavior?

You could update to the following if you want to thrown an exception in either of those cases.

  final matchingBuckets = bucketNames.where((name) => regex.hasMatch(name));
  if (matchingBuckets.length != 1) {
    throw Exception(...);
  }
  return matchingBuckets.single;

[Equartey]

Good suggestion! Cleaned this up using your approach. We only want to throw if there are more than 1 bucket. If there isn't a bucket we want to create one.

[Jordan-Nelson]

Note: We should discuss when the tests with gen1/cdk are removed. They add some benefit as they test that we are still properly supporting Gen 1 config formats. Integration tests are not an efficient way to test that though. If we feel good about the mapping from Gen 1 -> Gen 2 we could probably remove them.