Function build_source 

pub async fn build_source(
    kind: &str,
    config: Value,
    auth: &AuthCatalog,
    retry_policy: Option<&RetryPolicy>,
) -> CliResult<Box<dyn Source>>

Build a Source trait object from a (kind, config) pair. When the config carries auth: { ref: <name> }, the named provider is resolved from auth (the catalog) and injected into the connector.