Fix adding objects to a trip

[sixcare]

As of now the state of adding objects to a trip (creating references between trip and an object) is in a half working state.

It needs:

• Proper returning of trip with references to objects
• Tests for adding references
• Tests for removing references
  Implement API endpoint for removing a note_, route, or item_list_referance from a trip #428
• Sanity checks for adding references
  Implement check for double adding note_, route_, item_list_, refereances to an existing trip #427
• Ensure trip_id to look up is int