Incorrect center field type

[nyurik]

The center field is declared as center: Option<Vec<i32>>, which does not match specification:

OPTIONAL. Array. Default: null.
The first value is the longitude, the second is latitude (both in WGS:84 values), the third value is the zoom level as an integer. Longitude and latitude MUST be within the specified bounds. The zoom level MUST be between minzoom and maxzoom. Implementations MAY use this center value to set the default location. If the value is null, implementations MAY use their own algorithm for determining a default location.

{
  "center": [ -76.275329586789, 39.153492567373, 8 ]
}

Possible solutions

I think we should use this opportunity to improve the bounds value as well.

tuple

center: Option<(f32, f32, u8)>,
bounds: Option<(f32, f32, f32, f32)>,

structured

Per serde-rs/serde#637, uses serde_tuple crate.

#[derive(Serialize_tuple, Deserialize_tuple)]
struct Center {
  pub longitude: f32, 
  pub latitude: f32, 
  pub zoom: u8, 
}

#[derive(Serialize_tuple, Deserialize_tuple)]
struct Bounds {
  pub left: f32, 
  pub bottom: f32, 
  pub right: f32, 
  pub top: f32, 
}

...
center: Option<Center>,
bounds: Option<Bounds>,