ContentTranslationContextualLinksTest should use API calls to set up translation

What I don't understand is that when I run this test on 10.1.x, I can't see the contextual link that this line is testing:

> $link = $this->assertSession()->waitForElement('css', '[data-contextual-id^="node:node=1"] .contextual-links a:contains("Translate")');

> ->setLanguageAlterable(TRUE) is equivalent for $edit['settings[node][page][settings][language][language_alterable]'] = TRUE;. Don't we wan't to find the equivalent for 'settings[node][page][translatable]' ?

I'm cribbing from kernel tests, e.g. in EntityDefaultLanguageTest:

    $content_type = $this->container->get('entity_type.manager')->getStorage('node_type')->create([
      'name' => 'Test ' . $name,
      'title_label' => 'Title',
      'type' => $name,
      'create_body' => FALSE,
    ]);
    $content_type->save();
    ContentLanguageSettings::loadByEntityTypeBundle('node', $name)
      ->setLanguageAlterable(FALSE)
      ->setDefaultLangcode($langcode)
      ->save();

Tested fine for me.

## Test:

- Installed on Drupal 10.1
- Added all core language module
- Install Japanese language
- Change site to Japanese
- Create new page content in Japanese

Yes, please. Changes in the MR look great. This not only saves a form submit, but also a pointless login and logout. 🎉 Tests are still passing. MR needed a trivial rebase (which I did via the GitLab UI). But also recording here that I reviewed the diff and support this change.

Should be rebased again, but I agree with @dww, this is a good improvement.

Rebased.

Committed/pushed to 11.x, cherry-picked to 10.1.x and 10.0.x, thanks!

Automatically closed - issue fixed for 2 weeks with no activity.