feature: discover migrations

[joelbutcher]

TL;DR

This PR allows developers to specify whether their package should auto-discover all migrations in their package without having to specify individual file names.

Context – What problem does this solve?

For smaller packages with maybe a handful of migrations, calling hasMigration multiple times (or just hasMigrations once) is trivial and non-invasive.

However for larger packages, or for people using this tool in larger projects (e.g. registering composer modules in a large-scale production application), having to specify the name of every migration that is within a package or module becomes arduous and prone to mistakes

For example, newer developers will not necessarily always remember that each migration must be manually registered in a service provider (especially since Laravel's functionality is to auto-discover migrations).

Solution

This PR allows developers to choose whether or not their package "auto-discovers" its own migrations, by expanding the Package API with a new discoversMigrations method.

Developers and teams can now simply build a new package with as many migrations as they like without needing to remember to manually register the migration:

$package
    ->name('your-package-name')
    ->discoversMigrations();

When this is called, we will assume this is the default and that any calls to hasMigration or hasMigrations can safely be ignored. (If not, then in some scenarios, this would cause duplicate migrations and errors after publishing migrations and running artisan migrate).

$package
    ->name('your-package-name')
    ->hasMigration('create_my_package_tables') // Ignored
    ->hasMigrations(['my_package_tables', 'some_other_migration'])  // Ignored
    ->discoversMigrations();

I've also updated the hasMigrations to call discoversMigrations when no migration names are provided

[erikgaal]

Maybe add a (default) parameter of database/migrations so that you could technically discover it from elsewhere.

Never mind, that folder is already assumed. 🙃