Use serializer over as_json (forem#13029)

app/serializers/search/username_serializer.rb

@@ -0,0 +1,8 @@
+module Search
+  class UsernameSerializer < ApplicationSerializer
+    attributes :id,
+               :name,
+               :profile_image_90,
+               :username
+  end
+end

app/services/search/postgres/username.rb

@@ -11,22 +11,18 @@ class Username
       ].freeze
 
       def self.search_documents(term)
-        users = search_users(term)
+        results = ::User.search_by_username(term).limit(MAX_RESULTS).select(*ATTRIBUTES)
 
-        users.map do |user|
-          user.as_json(only: %i[id name username])
-            .merge("profile_image_90" => user.profile_image_90)
-        end
+        serialize(results)
       end
 
-      def self.search_users(term)
-        ::User
-          .search_by_username(term)
-          .limit(MAX_RESULTS)
-          .select(*ATTRIBUTES)
+      def self.serialize(results)
+        Search::UsernameSerializer
+          .new(results, is_collection: true)
+          .serializable_hash[:data]
+          .pluck(:attributes)
       end
-
-      private_class_method :search_users
+      private_class_method :serialize
     end
   end
 end

spec/services/search/postgres/username_spec.rb

@@ -13,7 +13,7 @@
       result = described_class.search_documents(user.username)
 
       expect(result.first.keys).to match_array(
-        %w[id name profile_image_90 username],
+        %i[id name profile_image_90 username],
       )
     end
 
@@ -35,7 +35,7 @@
       rhymes = create(:user, username: "rhymes")
 
       result = described_class.search_documents("ale")
-      usernames = result.map { |r| r["username"] }
+      usernames = result.pluck(:username)
 
       expect(usernames).to include(alex.username)
       expect(usernames).to include(alexsmith.username)
@@ -52,7 +52,7 @@
       results = described_class.search_documents("alex")
 
       expect(results.size).to eq(max_results)
-      expect([alex.username, alexsmith.username]).to include(results.first["username"])
+      expect([alex.username, alexsmith.username]).to include(results.first[:username])
     end
   end
 end