use BTreeMap;
/// Configuration for a named external source.
///
/// Parsed from `[sources.<name>]` in `cartulary.toml`:
/// ```toml
/// [sources.mygitlab]
/// type = "gitlab"
/// url = "https://gitlab.com"
/// project = "group/project"
/// token_env = "GITLAB_TOKEN"
///
/// [sources.mygitlab.status_map]
/// opened = "in-progress"
/// closed = "done"
/// ```