Implement assign DidHolder request

#1 (closed)

The solution/implementation of all HTTP operations performed by a business owner have the following definition-of-done checklist.

• The defined functional operation (see requirements)
• Enforces pre-conditions (these pre-conditions are a source of well-known errors)
• Exposes metrics
• Has a correct OpenAPI specification (that defines well-known errors)
• Has tests for:
  • happy path(s)
  • well-known errors