API: show if user is not mapped to any Bitbucket account (BB-9078)

Sometimes user commits to repo with different name and email address, usually after fresh install of git or mercurial. Let's say new username in raw hg commit is someone <name@example.com>. If the user has not mapped this email to his account, Bitbucket website says Author not mapped to Bitbucket user. when viewing the commit.

Example API request which is affected by this issue: {{GET repositories/

{accountname}

/

{repo_slug}

/changesets/

{raw_node}

/}}

It has fields
"raw_author": "someone <name@example.com>"
"author": "someone"

If the user is not mapped to any Bitbucket account, it is possible the author field contains some existing username that has nothing to do with the commit. In these cases I'd like to have a new boolean field isUserMapped so I can either use the author when it's mapped (for example to create a link to user account) or raw_author if user is not mapped.