Update coordinates

[mstoiakevych]

• Update coordinates representation to be like

"coordinates": [
    {
        "x": 1,
        "y": 1
    },
    {
        "x": 2,
        "y": 2
    },
   ...
]

instead of

"coordinates": [
    1, 1,
    2, 2
     ...
]

• Update the documentation
• Update tests