Refactor Geo::RepositoryVerificationFinder#find_outdated_projects

ee/app/finders/geo/repository_verification_finder.rb

 module Geo
   class RepositoryVerificationFinder
-    attr_reader :shard_name
-
     def initialize(shard_name: nil)
       @shard_name = shard_name
     end
 
     def find_outdated_projects(batch_size:)
-      cte_definition =
-        projects_table
-          .join(repository_state_table).on(project_id_matcher)
-          .project(projects_table[:id], projects_table[:last_repository_updated_at])
-          .where(repository_outdated.or(wiki_outdated))
-          .take(batch_size)
-
-      if shard_name.present?
-        cte_definition = shard_restriction(cte_definition)
-      end
+      query = build_query_to_find_outdated_projects(batch_size: batch_size)
+      cte   = Gitlab::SQL::CTE.new(:outdated_projects, query)
 
-      cte_table    = Arel::Table.new(:outdated_projects)
-      composed_cte = Arel::Nodes::As.new(cte_table, cte_definition)
-      alias_to     = Arel::Nodes::As.new(cte_table, projects_table)
-
-      Project.with(composed_cte)
-             .from(alias_to)
+      Project.with(cte.to_arel)
+             .from(cte.alias_to(projects_table))
              .order(last_repository_updated_at_asc)
     end
 
@@ -35,10 +21,7 @@ module Geo
          .where(repository_never_verified)
          .limit(batch_size)
 
-      if shard_name.present?
-        relation = shard_restriction(relation)
-      end
-
+      relation = apply_shard_restriction(relation) if shard_name.present?
       relation
     end
 
@@ -58,7 +41,21 @@ module Geo
       Project.verification_failed_wikis.count
     end
 
-    protected
+    private
+
+    attr_reader :shard_name
+
+    def build_query_to_find_outdated_projects(batch_size:)
+      query =
+        projects_table
+          .join(repository_state_table).on(project_id_matcher)
+          .project(projects_table[:id], projects_table[:last_repository_updated_at])
+          .where(repository_outdated.or(wiki_outdated))
+          .take(batch_size)
+
+      query = apply_shard_restriction(query) if shard_name.present?
+      query
+    end
 
     def projects_table
       Project.arel_table
@@ -97,7 +94,7 @@ module Geo
       Gitlab::Database.nulls_last_order('projects.last_repository_updated_at', 'ASC')
     end
 
-    def shard_restriction(relation)
+    def apply_shard_restriction(relation)
       relation.where(projects_table[:repository_storage].eq(shard_name))
     end
   end