[DO NOT MERGE] Translation Layer Template

[josvazg]

This is an example template that can help understand the gist of a translation layer, or even be used as a starting point to implement a translation layer for a new resource or refactor an existing one.

The important bits are in the packages internal/translation/resource & test/contract/resource

The rest is just there for completeness and should have been merged before this template is to be used.

Translation layer public interface:

• An resource interface with the operations the reconciliation would need to do on the resource.
  • All arguments and return types are internal and or Kubernetes CRDs.
• A way to create the internal version of the resource from the CRD and some attachments, like secrets, etc.
• A way to normalize the resource internal type defined in Kubernetes to allow it to be compered with the same type converted from Atlas.
• Optionally, the comparison function of internal resource types might also be defined in the translation layer.

Key features:

• The translation layer completely encapsulates the Atlas API interactions:
  • No Atlas API calls are exposed elsewhere in the code.
  • No Atlas API data types are used or imported anywhere else in the code. Nothing else imports the Atlas SDK.
• The translation layer is an internal package, not exposed to operator consumers.
  • Adding a translation layer does not affect the rest of the codebase util it is used.
• The translation layer allows for easy Contract Testing of each of the API endpoints encapsulated.
  • This enables easy Atlas behavior verification up front, even before the reconcilation state machine is coded.
• Other than that, unit testing of the type conversions, normalization and comparisons is also to be expected within this layer.

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