Experiment of ink! Smart Contract: Struct

This example smart contract is for testing purpose.

• Nested structs as parameter (Inner, Outer): Normal nested JSON object passed in through the API.
• Enum as parameter (Shape::Circle, Shape::Rectangle): Take Shape::Rectangle as example:

[
  {
    "Rectangle": [
      3,
      4
    ]
  }
]

or

[
  {
    "Rectangle": {
      "x": 3,
      "y": 4
    }
  }
]

Explanation: Specify the name of the enum variant in the JSON object's top-level entry. Then either pass in the fields in order or name the fields and specify the values in any order.