Attribute configuration no longer allows multiple attributes per pattern

[cab]

The type_attributes, field_attributes, etc methods are described as cumulative, but after this change there can only be one attribute per path.

It's not clear to me if this new behavior is the correct behavior or if the old behavior was unintentionally allowing this.

I think this is a regression from 79f0dfd. Previously, multiple values could exist with the same matcher, but now only one entry can exist in the PathMap's matchers hashmap.

Example

.type_attributes(".", "[derive(::serde::Serialize)]")
.type_attributes(".", "[serde(rename = \"camelCase\")]")

Before the regression (e.g. on 0.7), this would output

#[derive(::serde::Serialize)]
#[serde(rename = "camelCase")]
struct MyProto {}

After the regression, this outputs

#[serde(rename = "camelCase")]
struct MyProto {}

[cab]

if this is a regression, one possible fix might be making Config#type_attributes a PathMap<Vec<String>> and then adding something like this to PathMap:

pub(crate) fn extend<A>(&mut self, matcher: String, value: T) where T: Extend<A> + IntoIterator<Item = A> + Default {
    self.matchers.entry(matcher).or_default().extend(value);
}

[LucioFranco]

Fixed in #522