Function register_file_source 

pub fn register_file_source(
    registry: &ConnectorRegistry,
) -> Result<(), ConnectorError>

Registers the file source connector in the registry.

This is called by LaminarDB::register_builtin_connectors() when the files feature is enabled, and makes connector = 'files' available in CREATE SOURCE statements.

Errors

Returns an error if the connector name is already registered or the registry is frozen.