Logistics Object ID can optionally be set when creating a new LO

As a participant of the internet of logistics, I'd like to be able to provide an self-selected ID for a new LO.

Acceptance criteria

• If the POSTed LO already contains a preset ID, the server checks if it's valid and takes it as the ID of the newly created LO. Valid URLs:
  • No duplicate
  • The internal ID contains only characters A-Z,a-z,0-9,- and is prefixed with the base path of the server.
• If the contained ID is invalid (due to duplication), the server responds with status code 409. In general, a 401 is returned for invalid IDs.