Set sample item_tag position to 1

Without an explicit position, the sample row gets NULL, which Postgres
sorts last by default — surprising for a single-row first-run state and
fragile once a client adds more items without managing position
themselves. Setting position 1 gives the sample a definite slot and
keeps the (:position, :name) sort meaningful for clients that don't
implement reordering.

Author: dadachi

app/models/shop.rb

@@ -17,6 +17,7 @@ def create_sample_item_tag
       account: account,
       name: "Sample",
       description: "This is a sample. You can update or delete it.",
+      position: 1,
       created_by: created_by
     )
   rescue => e

test/models/shop_test.rb

@@ -36,6 +36,7 @@ def setup
       sample = shop.item_tags.first
       assert_equal "Sample", sample.name
       assert sample.description.start_with?("This is a sample")
+      assert_equal 1, sample.position
       assert sample.idled?
     end
   end