The name query parameter to UserPasswordForm can result in lots of cache entries

The logic around this has changed a bit since #2828724: Username enumeration via one time login route → .

More specifically, I can't see anywhere that we actually pass the name query parameter to this form, so I'm wondering if we can just remove support for the query arg and setting the default value entirely.

The last submitted patch, 19: 2828210.patch, failed testing. View results →

OK we do use it as the test coverage shows:

  $query = isset($user_input['name']) ? ['name' => $user_input['name']] : [];
        $form_state->setErrorByName('name', $this->t('Unrecognized username or password. <a href=":              password">Forgot your password?</a>', [':password' => Url::fromRoute('user.pass', [], ['query' => $query])-      >toString()]));

From UserLoginForm::validateFinal().

for avoid having lots of cache entries for the UserPasswordForm class with different values for the name query parameter. So adding cache metadata for the name query parameter after that setting the cache context to url.query_args:name and setting the cache tags will invalidate the cache when the user with the given name is updated. Not adding Interdiff as patch is following different approach.