Import generated directory structure invalid for python import with dashes

[gabe-l-hart]

Description of the bug:

When running cdk8s import against a CRD whose custom resource group name contains dash characters (-), the resulting directory structure also contains dashes in the directory names. For a python app, this is invalid for import, making the resulting package unreachable from within the python code.

Reproduction Steps:

1. In the crd example, update the version.yaml file so that the group is sample-controller instead of samplecontroller
2. Run cdk8s import version.yaml

3. tree imports

   imports/
   └── sample-controller
       └── k8s
           └── io
               └── foo
                   ├── __init__.py
                   ├── _jsii
                   │   ├── __init__.py
                   │   └── generated@0.0.0.jsii.tgz
                   └── py.typed
   
   5 directories, 4 files

4. python -c 'from imports.sample-controller.k8s.io import foo'

Error Log:

  File "<string>", line 1
    from imports.sample-controller.k8s.io import foo
                       ^
SyntaxError: invalid syntax

Environment:

• Framework Version:

  0.25.0

• OS: MacOS

Other:

I'm fairly certain I have a fix, but I haven't gotten the test env set up and have been distracted with other items this morning. I think that this section needs to do a replace of - with _. I'll keep this ticket up to date with anything else I find while testing.

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This is :bug: Bug Report

[campionfellin]

@iliapolo I can take this, as it's so closely related to https://github.com/awslabs/cdk8s/issues/273