When we are updating models via GraphQL, we assign new attribute values to the model and save (BaseMutation#save_object).
If there are validation errors, the model with invalid attribute values is used for response. This is causing problems in UI with as Apollo detects a change in an attribute and places the new (invalid) value into its cache. To leverage Apollo's automatic cache updates, we should return the persisted value, not the assigned and invalid.

Steps to reproduce:

variables = { id: model_global_id, name: '' }

mutation UpdateModelMutation($id: ID!, $name: String) {
  updateModel(input: { id: $id, name: $name }) {
    model {
      id
      name
    }
    errors {
      path
      message
    }
  }
}

Expected Result:

{
  updateModel {
    model {
      id: 'very_long_global_id',
      name: 'My model'
    },
    errors: [{
     path: ["attributes", "name"],
     message: "can't be blank" 
   }]
  }
}

Actual Result:

{
  updateModel {
    model {
      id: 'very_long_global_id',
      name: ''
    },
    errors: [{
     path: ["attributes", "name"],
     message: "can't be blank" 
   }]
  }
}