Error for duplicated record keys

[ypyl]

Closes #24

[MaybeJustJames]

Thanks @ypyl for your help with this :)

[ypyl]

@MaybeJustJames do you think it will be useful to have a list of duplicated keys in the error message?

I am having an issue showing the user where duplicated keys are as the error looks like this:

Line 54, column 1: Problem: Non-unique keys in record

The yaml file looks like (ring-1 is duplicated). So Line 54, column 1 doesn't make sense to me.

domain:
  name: Name
  description: Description
  actors:
    actor-1:
      name: Actor
      description: Description
      relations:
        - uses - delivery-1
  rings:
    ring-1:
      name: Ring 1 name
      description: Description
      relations: []
      deliveries: {}
    ring-1:
      name: Ring 2 name
      description: Description
      relations:
        - uses - ring-1
      deliveries:
        delivery-1:
          name: delivery 1
          description: Description
          relations:
            - calls - delivery-2
            - uses - ring-1
          blocks:
            delivery-1--block-1:
              name: block 1
              description: Description
              relations:
                - uses - delivery-1--block-2
                - calls - delivery-2--block-1
                - uses - ring-1
            delivery-1--block-2:
              name: block 2
              description: Description
              relations: []
        delivery-2:
          name: delivery 2
          description: Description
          relations: []
          blocks:
            delivery-2--block-1:
              name: block 1
              description: Description
              relations:
                - uses - delivery-2--block-2
            delivery-2--block-2:
              name: block 2
              description: Description
              relations: []
views:
  view-1:
    elements:
      ring-1:
        x: 100
        y: 100
      delivery-1:
        x: 200
        y: 200
        relations:
          calls - delivery-2:
            - x: 300
              y: 150
          uses - ring-1: []
      delivery-2:
        x: 300
        y: 300
  view-2:
    elements:
      actor-1:
        x: 100
        y: 100
        relations:
          uses - delivery-1: []
      delivery-1:
        x: 200
        y: 200