Add ability to attach additional databases in SQLite

[bpedroza]

Proposal

Add ability to attach additional databases in SQLite:
SQLite provides functionality to allow attaching multiple databases. The syntax to make this attachment is pretty simple: ATTACH DATABASE file_name AS database_name . This allows making queries against SQLite using dot notation in table names.

Why though?

We are using SQL Server as our primary database and tables exist in schemas, so a query could be select * from products.sizes where products.sizes.size in ('sm', 'md') when attempting to create the schema in SQLite this blows up. saying database products not found.

Adding this functionality would allow creating another SQLite database products and tell the connector to attach it via configuration variable when the connection is created.

This would provide a significant improvement in developer experience for people using production databases that support schemas in this way.

Implementation

I have got this working locally and would be glad to implement and submit a PR. My thoughts are to add a new configuration key for database.connections.sqlite maybe attached_databases which would be an array where keys are the alias and values are the database location:

'connections' => [

	'sqlite' => [
		'driver'   => 'sqlite',
		'database' => database_path('database.sqlite'),
		'prefix'   => '',
		'attached_databases' => [
			'products' => database_path('products.sqlite'),
                        'teams' => database_path('teams.sqlite'),
	]	
],

This could be implemented in Illuminate\Database\Connectors\SQLiteConnector::connect before returning the connection.

Thanks for your consideration.