Function parse 

pub fn parse(
    source_name: &str,
    toml_text: &str,
    canonical: impl Fn(ResourceKind) -> RelPath,
) -> Result<Provider, ManifestError>

Parses and validates a provider manifest.

source_name is used purely for diagnostics — typically the file name. canonical supplies the canonical path per resource so that native declarations can be checked against reality rather than trusted.