Re-factored code to CQRS

[Ceredron]

Description

Preparation to improve logging consistency.
Re-factored code to CQRS to move business logic out of controllers. Separating the business layer from API layers makes it easier to reason about the code, helps us avoid bugs and isolates different concerns by project.

For more on CQRS:
https://learn.microsoft.com/en-us/azure/architecture/patterns/cqrs

Related Issue(s)

• Bygg en grunnmur for logging #186

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)