Make shield work with core basic_auth

Cross reference, please also see: https://www.drupal.org/project/shield/issues/2815945

composer did not like that patch file, new one attached

try that again, no contrib

not working correct, there is a race condition that is causing intermittent problems

Please restore the spacing in this patch. It's difficult to review as-is. I suspect a lot less has changed than is showing here.

Ported this same patch to the newest dev version of Shield. Tested with Shield 8.x-1.2.

This looks similar to the related issue. Please consolidate.
Also going to commit patches touching this code, so probably needs reroll.

I rerolled the patch as the MR.

With the latest fixes the last issue is this test failure:

  public function testShieldWithBasicAuth() {
    // Configure shield, so it is enabled and basic_auth headers are kept.
    // We don't need to test the case with unset_basic_auth_headers to TRUE
    // as it is the default value, it is tested by testShieldCred().
    $this->config('shield.settings')
      ->set('shield_enable', TRUE)
      ->set('unset_basic_auth_headers', FALSE)
      ->save();

    $this->drupalGet('user', [], ['Authorization' => 'Basic ' . base64_encode('user:password')]);
    $this->assertSession()->statusCodeEquals(403);
  }

The problem here is that it suggests the changes aren't working at all?

I just realized that there's no way of controlling the "unset_basic_auth_headers" setting, so it might be worth adding a separate issue for that.

Basic Auth in core (for Drupal users is a great idea, but since you can only pass the basic auth parameters once, the user login needs to be tied to shield.

Created an MR that, if core basic_auth is enabled, allow an administrator to enable basic_auth as an option inside shield. This resolves most of the issues found above, and resolves a feature request in #2827060: Allow to authenticate with user credentials