Refactoring of domain models and contracts

[MGTheTrain]

Checklist

• I adhere the trunk-based workflow
• I verify that the CHANGELOG.md includes comprehensive documentation for the implemented features or fixed bugs. Increment the minor version such as from 0.1.0 to 0.2.0 for implemented features and increment the patch version from 0.1.0 to 0.1.1 for bug fixes. If any breaking changes occur, increment the major version, like from 0.1.0 to 1.0.0. Also see Semantic Versioning 2.0.0
• I ensure that all merge conflicts are resolved before asking for a PR reviewer
• To ensure the success of all pull request workflows, I run the format-and-lint.sh and run-test.sh locally.

Reference/Link to the issue solved with this PR (if any)

• Refined service contracts
• Added services structs
• Renamed domain model structs