add error structure for users #191

[rago89]

Hello, I've made, the code structure error for the user API, could you please take a look, I'll make animals after acceptance criteria in users

[dirk-jacobs]

Not yet

Current return on 4xx: { message: ${error.name} ${error.message} }

Expected: Something like { code: ${error.code}, message: ${error.message} }