Mongoose Model Custom Error Message for Enums

Try something like it:

var enu = {
  values: ['pending', 'accept', 'decline']
, message: 'Status is required.'
}


var ConnectionRequestSchema = new Schema({
  ...

  status: {
    type: String
  , enum: enu
  , trim: true
  }
});

difficulty: {
        type: String,
        required: [true, 'A tour must have a difficulty.'],
        enum: {
            values: ['easy', 'medium', 'difficult'],
            message: 'Difficult is either easy, medium, difficult.'
        }
    }