Ultimike 3.0.x patch 77216

I believe this change fixes a large portion of this issue, in that a mostly correct page is now loaded when the user clicks the "Add existing content" or "Add new content" buttons on /group/{group_id}/nodes

This doesn't completely fix things though because ideally, when going to /group/{group_id}/content/add from this "Nodes" page, the only options should be to add nodes. As it stands now, this page displays the option to add both nodes and members.

I'm not sure why, but the $copy->setDefault('base_plugin_id', 'group_node'); lines are not working here. I spent a good amount of time in xdebug trying to figure out why the base_plugin_id value isn't being passed into Drupal\group\Entity\Controller\GroupRelationshipController::addPage() correctly, to no avail. If someone else can figure out where the issue lies, I would be most appreciative.

I can confirm the correct behavior would result if the base_plugin_id value reaches addPage() successfully, assuming that https://www.drupal.org/project/group/issues/2842630 is also committed as well.

-mike