Allow table inspection when the database connection config is generated on the fly.

[rabrowne85]

Summary

For applications were the developer is using a multi-tenancy setup, utilising multiple databases i.e., one for the landlord and many for the tenants, the database config definition is usually altered by the multi-tenancy package when a new tenant is activated.

This however, means that the database.connections.tenant config is usually missing a value for database.connections.tenant.database so laravel-ide-helper cannot connect to the database to inspect the properties.

This modification adds a new config entry into the ide-helper.php config file that allows for overrides for the database.connections array to be set. When the model generator command is run, these overrides are set in the in-memory config values, such that when the connection is used to inspect the database schema, it has the full information. However, this doesn't have a knock on effect that the database.php config file needs to be constantly altered and then reset.

The user can also elect to use an env() value in the ide-helper.db_connections_override array so that between developers the database name can be set as needed.

This has been referenced in the following issues:
#1141
#1280

An attempt at a pull request #1285 was submitted by vpratfr which attempts a similar idea, but requires specifying a specific connection to use and alters the connection logic. I can see that this could have "breaking" implications and makes things difficult to test. This PR uses the existing connections and allows for the user to specify a database name (in essence) i.e., it's there if the user wants to use it, but if not nothing really changes.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Misc. change (internal, infrastructure, maintenance, etc.)

Checklist

• Existing tests have been adapted and/or new tests have been added
• Add a CHANGELOG.md entry
• Update the README.md
• Code style has been fixed via composer fix-style