Use clearer names for variable and methods when locking polled candidates

The name `lock` alone was confusing because it's the same as ActiveRecord's lock
method, and `candidates` was a bit ambiguous, easy to say explicitly that the candidates
are job IDs.

Author: rosa

app/models/solid_queue/ready_execution.rb

@@ -18,18 +18,19 @@ def select_and_lock(queue_relation, process_id, limit)
           return [] if limit <= 0
 
           transaction do
-            candidates = select_candidates(queue_relation, limit)
-            lock(candidates, process_id)
+            job_ids = select_candidates(queue_relation, limit)
+            lock_candidates(job_ids, process_id)
           end
         end
 
         def select_candidates(queue_relation, limit)
           queue_relation.ordered.limit(limit).lock("FOR UPDATE SKIP LOCKED").pluck(:job_id)
         end
 
-        def lock(candidates, process_id)
-          return [] if candidates.none?
-          SolidQueue::ClaimedExecution.claiming(candidates, process_id) do |claimed|
+        def lock_candidates(job_ids, process_id)
+          return [] if job_ids.none?
+
+          SolidQueue::ClaimedExecution.claiming(job_ids, process_id) do |claimed|
             where(job_id: claimed.pluck(:job_id)).delete_all
           end
         end