Feature/simple request submission persistance

The changes to the checklist: gaia-x/data-infrastructure-federation-services/not/notarization-service#2

• The defined functional operation (see requirements)
• Enforces pre-conditions (these pre-conditions are a source of well-known errors)
• Exposes metrics
• Audits the operation will be handled in its own issue
• Has a correct OpenAPI specification (that defines well-known errors)
• Has tests for:
  • happy path(s)
  • well-known errors