use 5.026;
package MyModule::Config {
    use Mouse;
    has text => (is => 'ro', isa => 'MyModule::Config::Text');
}

package MyModule::Config::Text {
    use Mouse;
    has Name => (is => 'ro');
}

my $c = MyModule::Config->new(
    text => MyModule::Config::Text->new(Name => 'Wert')
);

say $c->text->Name; # 'Wert'