This change enables users to set display names for assets in their pipelines, to make Asset steps in CodePipeline easier to parse. Instead of having 'FileAssetN' and 'DockerAssetN' actions in these steps, users could have descriptive names for these assets like 'GetProfile' or 'AddToCart'.

For a user, this would consist of using the new displayName properties in the Asset, TarballImageAsset and DockerImageAsset constructs, like so:

new s3_assets.Asset(stack, 'MyNamedFile', {
  path: path.join(__dirname, 'assets'),
  displayName: 'some-name',
});

Implementation of this feature involves following the whole lifecycle of an asset. From the moment of instantiation to the generation of manifests and later parsing these manifests while building the pipeline. To avoid changing method signatures I opted to add a new optional property displayName in the FileSource and DockerImageSource interfaces. This property is passed all the way down to the AssetManifestBuilder, where it's persisted into the file manifest.

This required modifying the schema of the asset manifest. AFAIK, this change can not be implemented without adding information to it. The only possible spot for this display name without changing the schema would be in an asset's key, which normally is a hash and may be used by other methods to detect wether the asset should be reuploaded.

This feature includes changes to the aws-s3-assets and aws-ecr-assets to enable passing of the displayName property to them. Higher level constructs (like NodejsLambda) will require some wiring to pass these same properties lower into the tree to their used 'base types' (Asset, TarballImageAsset and DockerImageAsset). I might include this use case into the PR before finishing the draft.

TODO:

• Add integration test
• Change README
• Add wiring for higher level constructs (aws_lambda_nodejs, aws-lambda-python-alpha and aws-lambda-go-alpha). This might be scope creep, so feedback would be appreciated if you'd rather review this PR as-is and have these implementations in another PR.
• Add validation for the displayNames in the lower-level Constructs. Right now, spaces in names are replaced with underscores. Not documenting or throwing errors with this would be confusing for users.

Closes #9628.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license