Function resolve_user 

pub async fn resolve_user(
    client: &Client,
    slug: &RepoSlug,
    query: &str,
    extra: &[User],
) -> Result<User>

One human-typed name to one user.

A {uuid} is already exact and is taken verbatim, with no api call. Anything else is matched case-insensitively as a substring of the display name or nickname. Emails are not accepted: a reviewer is written to the api as a uuid, and bitbucket’s member listings do not expose email addresses, so an email could never be resolved — failing here beats failing inside a write.