public function up()
    {
        Schema::table('users', function (Blueprint $table) {
            if (Schema::hasColumn('users', 'name'))
                $table->dropColumn('name');
            $table->integer('role_id')->unsigned()->nullable();
            $table->foreign('role_id')->references('id')->on('roles')->onDelete('cascade');
            $table->string('firstname')->default('');
            $table->string('lastname')->default('');
            $table->string('picture')->nullable();
        });
    }