Breaking changes: change select options to (key, value) tuple

[awarecan]

For dict

vol.Schema(vol.In({'key1': 'value1', 'key2': 'value2'})
==>
{
  'type': 'select',
  'options': [
    ('key1', 'value1'),
    ('key2', 'value2'),
  ]
}

And it can covert to JSON

{
  "type": "select",
  "options": [
    ["key1", "value1"],
    ["key2", "value2"]
  ]
}

For list, key and value is same

vol.Schema(vol.In(['value1', 'value2'])
==>
{
  'type': 'select',
  'options': [
    ('value1', 'value1'),
    ('value2', 'value2'),
  ]
}

Therefore, it can better support dropdown selection.

[balloob]

The value of options should always be the same. I suggest that if a non-mapping is given, both key and value are the same.

[balloob]

You can just write list(schema.container.items())