Allow to reparent Quantity everywhere

Closes #61

app/controllers/application_controller.rb

@@ -43,6 +43,11 @@ class ApplicationController < ActionController::Base
 
   private
 
+  def render_no_content(record)
+    helpers.render_errors(record)
+    render html: nil, layout: true
+  end
+
   def rescue_turbo(exception)
     raise unless request.format.to_sym == :turbo_stream
 

app/controllers/quantities_controller.rb

@@ -43,7 +43,8 @@ class QuantitiesController < ApplicationController
     permitted = params.require(:quantity).permit(:parent_id)
     @previous_ancestors = @quantity.ancestors
 
-    @quantity.update!(permitted)
+    # Until UI blocks all disallowed reparents, render error messages if present
+    render_no_content(@quantity) unless @quantity.update(permitted)
 
     @ancestors = @quantity.ancestors
     @quantity.depth = @ancestors.length