Add a field to a Stream in PyroCMS 3

pyrocms_migration.php

<?php

use Anomaly\Streams\Platform\Database\Migration\Migration;

class MyprojectModuleIndividualsAddSlugField extends Migration
{
    /* Define the new field, and field config here */
    protected $fields = [
        'slug' => [
            'type' => 'anomaly.field_type.slug',
            'config' => [
                'type'    => '-',
                'slugify' => 'name'
            ]
        ]
    ];

    /* Choose which stream this is being applied to */
    protected $stream = [
        'slug' => 'individuals'
    ];

    /* Define the stream assignments */
    protected $assignments = [
        'slug' => ['required' => 'true'],
    ];

    /* Do any processing on existing entries if needed */
    public function up()
    {
        $individuals = \Myproject\IndividualsModule\Individual\IndividualModel::all();

        foreach($individuals as $individual){
            $individual->slug = str_replace(" ", "-", strtolower($individual->name));
            $individual->save();
        }
    }
}