Change how hashtags are normalized (#18795)

* Change how hashtags are normalized

* Fix tests

db/migrate/20220710102457_add_display_name_to_tags.rb

@@ -0,0 +1,5 @@
+class AddDisplayNameToTags < ActiveRecord::Migration[6.1]
+  def change
+    add_column :tags, :display_name, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_07_04_024901) do
+ActiveRecord::Schema.define(version: 2022_07_10_102457) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -940,6 +940,7 @@ ActiveRecord::Schema.define(version: 2022_07_04_024901) do
     t.datetime "last_status_at"
     t.float "max_score"
     t.datetime "max_score_at"
+    t.string "display_name"
     t.index "lower((name)::text) text_pattern_ops", name: "index_tags_on_name_lower_btree", unique: true
   end