Make `Polygon` fields public.

[gibbz00]

Polygon::{exterior,interiors}_mut() are for example insufficient when using closures that return a Result.

I do realize that this might cause issues with polygons that aren't closed if instantiation is created without the proper new constructor, so there's probably a better way to go about this. I simply chose the method that resulted in the least amount of changes possible.

Example:

/// Old
impl Transform for Polygon {
    fn transform_coordinates<F: TransformClosure>(&mut self, f: &mut F) -> Result<()> {
        let (mut exterior, mut interiors) = self.clone().into_inner();
        exterior.transform_coordinates(f)?;
        interiors
            .iter_mut()
            .try_for_each(|line_string| line_string.transform_coordinates(f))?;
        *self = Polygon::new(exterior, interiors);
        Ok(())
    }
}

/// New
impl Transform for Polygon {
    fn transform_coordinates<F: TransformClosure>(&mut self, f: &mut F) -> Result<()> {
        self.exterior.transform_coordinates(f)?;
        self.interiors
            .iter_mut()
            .try_for_each(|interior| interior.transform_coordinates(f))
    }
}

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• [X] I agree to follow the project's code of conduct.
• [X] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

[frewsxcv]

Right now Polygon is guaranteed to be close, and by publicizing the fields we lose that guarantee. I'd rather explore other options to increase ergonomics and keep our guarantee before resorting to this.

[gibbz00]

Right now Polygon is guaranteed to be close, and by publicizing the fields we lose that guarantee. I'd rather explore other options to increase ergonomics and keep our guarantee before resorting to this.

Gotcha. Got an alternative solution to work. Sending in a new PR soon.