How do you generate a motion plan from moveit_msgs::MotionPlanRequest and moveit_msgs::MotionPlanResponse?

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So I found the answer and I'll share it here in case anyone finds it helpful. The Pilz Tutorial gives you two options: The MoveGroup Action and the /plan_kinematic_path service. Both of these should start up when you start the movegroup node. I used the /plan_kinematic_path to generate a PILZ trajectory and the movegroup interface to execute that trajectory. It seems that this should work with other planning plugins, or atleast ones that develop kinematic paths. i.e

moveit::planning_interface::MoveGroupInterface::Plan plan; 
moveit_msgs::MotionPlanRequest req;
moveit_msgs::MotionPlanResponse res;

Fill out the request as shown in the tutorial. I formed the goal constraints using

moveit_msgs::Constraints pose_start_goal = kinematic_constraints::constructGoalConstraints(end_link, pose_stamped, tolerance_pos, tolerance_ang);

and then I instantiated the service client, filled the request and called the service:

ros::ServiceClient motionplanclient = nh.serviceClient<moveit_msgs::GetMotionPlan>("/plan_kinematic_path");
plan_path.waitForExistence();
moveit_msgs::GetMotionPlan motionplansrv;
motionplansrv.request.motion_plan_request = req;
motionplanclient.call(motionplansrv);

Then I pulled the response from the service and added the trajectory to the plan

res=motionplansrv.response.motion_plan_response;
plan.trajectory_=res.trajectory;

I used rviz_visual_tools to publish the trajectory visual_tools.publishTrajectoryLine(plan.trajectory_, joint_model_group) and move_group.execute(plan) to move the robot.

My current issue is now with MotionSequenceRequest, namely visualizing the path in RVIZ and executing the plan, but I'll post that as another question and link it here.