Add a clear_in_batches method to delete recurring executions

This is useful for those who decide not to have FKs that ensure recurring
executions are deleted when jobs are cleared up, so they can just
call this method periodically to clear orphaned executions.

Author: rosa

app/models/solid_queue/recurring_execution.rb

@@ -2,14 +2,25 @@
 
 module SolidQueue
   class RecurringExecution < Execution
-    def self.record(task_key, run_at, &block)
-      transaction do
-        if job_id = block.call
-          create!(job_id: job_id, task_key: task_key, run_at: run_at)
+    scope :clearable, -> { where.missing(:job) }
+
+    class << self
+      def record(task_key, run_at, &block)
+        transaction do
+          if job_id = block.call
+            create!(job_id: job_id, task_key: task_key, run_at: run_at)
+          end
+        end
+      rescue ActiveRecord::RecordNotUnique
+        SolidQueue.logger.info("[SolidQueue] Skipped recurring task #{task_key} at #{run_at} — already dispatched")
+      end
+
+      def clear_in_batches(batch_size: 500)
+        loop do
+          records_deleted = clearable.limit(batch_size).delete_all
+          break if records_deleted == 0
         end
       end
-    rescue ActiveRecord::RecordNotUnique
-      SolidQueue.logger.info("[SolidQueue] Skipped recurring task #{task_key} at #{run_at} — already dispatched")
     end
   end
 end