restructured protobuf generated code

[xh3b4sd]

abstract

This PR goes towards #243 and #244.

checklist

• [x] Make sure you read and understood the CONTRIBUTING.md.
• [x] Make sure you applied sufficient labels, milestone and assignee.
• [x] Make sure all TODOs are addressed.
• [x] Make sure there is sufficient documentation.
• [x] Make sure there are sufficient tests.
• [x] Make sure all commits are squashed before merging.
• [x] Make sure to delete the feature branch after merging.

[codecov-io]

Current coverage is 91.99% (diff: 100%)

Merging #256 into master will not change coverage

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