Function mark_installing 

pub fn mark_installing(
    conn: &DbConnection,
    name: impl Into<String>,
    version: impl Into<String>,
    kind: InstallerType,
    deployment_kind: DeploymentKind,
    engine_kind: EngineKind,
    install_dir: &Path,
) -> Result<()>

Insert a package record marked as installing.

The record captures the package metadata and provisional install directory so the database reflects that work is in progress before the payload download starts.