Create "Node links" block

Thanks!

1. +++ b/src/Plugin/Block/NodeLinks.php
   @@ -0,0 +1,105 @@
   + *   category = @Translation("Node"),
   

   Category should probably be "Content" since that's what we're using for the other blocks that need a node context.

2. +++ b/src/Plugin/Block/NodeLinks.php
   @@ -0,0 +1,105 @@
   + *     "node" = @ContextDefinition("entity:node", label = @Translation("Node"), required = TRUE)
   

   Here too - we use "Content" in the label of other context that take nodes.

3. +++ b/src/Plugin/Block/NodeLinks.php
   @@ -0,0 +1,105 @@
   +    $options = $this->viewModeStorage->loadByProperties([
   +        'targetEntityType' => 'node',
   +      ]);
   +    foreach ($options as $option) {
   +      $form['view_mode']['#options'][$option->id()] = $option->label();
   +    }
   

   Hm. So, I don't know which way is better, but I would have used \Drupal::service('entity_type.bundle.info')->getBundleInfo('node') (except properly injected :-)) to get the list of view modes. Directly accessing the config entities seems like we're skipping an abstraction - but maybe it's fine?

   We should get some feedback from someone who knows the Entity Field API better...

4. +++ b/src/Plugin/Block/NodeLinks.php
   @@ -0,0 +1,105 @@
   +    return NodeViewBuilder::renderLinks($node->id(), $this->configuration['view_mode'], $node->langcode->value, FALSE);
   

   Whoa! Super cool that we don't have to duplicate the code here. :-)

Actually, thinking about #6.3 some more - I think it's possible for a view mode to exist, but have no config entity for it! This is when the user chooses not to enable custom display settings for a view mode, and the settings for "Default" are re-used. We don't want to have to change block settings depending on if view mode has custom settings or not - we should just set the view mode and the correct display settings get used.

So, I think we should definitely use the 'entity_type.bundle.info' service to get the list of view modes, rather than the config entity.

Thanks! I still think we should switch to the bundle info per #6.3, but I'd like to do some testing to see if the result is different. I suspect that getting the config entities will be missing the view modes that aren't customized, and we want to be able to select all views, not just the customized ones.