Background migrations CLI

What does this MR do and why?

This MR implements the following rake tasks

• gitlab:background_migrations:list - List all background migrations (across all databases)

  $ bundle exec rails gitlab:background_migrations:list
  
  id      | table_name                                              | job_class_name                                              | status   
  --------|---------------------------------------------------------|-------------------------------------------------------------|----------
  main_1  | namespace_settings                                      | UpdateRequireDpopForManageApiEndpointsToFalse               | finished 
  main_2  | resource_iteration_events                               | BackfillResourceIterationEventsNamespaceId                  | finalized
  main_3  | identities                                              | DeleteTwitterIdentities                                     | finalized
  main_4  | software_license_policies                               | BackfillLicensesOutsideSpdxCatalogue                        | finalized
  main_5  | security_policies                                       | BackfillPipelineExecutionPoliciesMetadata                   | finished 
  ci_1    | ci_runners                                              | MarkAdminBotRunnersAsHosted                                 | finalized
  ci_2    | p_ci_build_trace_metadata                               | BackfillUpsertedCiBuildTraceMetadataProjectId               | finalized
  ci_3    | ci_runners                                              | BackfillOrganizationIdOnCiRunners                           | finalized
  ci_4    | ci_runner_machines                                      | BackfillOrganizationIdOnCiRunnerMachines                    | finalized
  ci_5    | ci_runner_taggings                                      | BackfillOrganizationIdOnCiRunnerTaggings                    | finalized

  id has a format of {db}_{id} so that it contains all the information required, while still easy to copy/paste. This makes it easier to use the tasks to manage specific migration.

• gitlab:background_migrations:show[id] - show migration details

  $ bundle exec rails gitlab:background_migrations:show[ci_1]
  
  id                       | ci_1                       
  created_at               | 2025-05-06 22:40:08 UTC    
  updated_at               | 2025-08-20 22:29:07 UTC    
  min_value                | 1                          
  max_value                | 30                         
  batch_size               | 1000                       
  sub_batch_size           | 100                        
  interval                 | 120                        
  status                   | finalized                  
  job_class_name           | MarkAdminBotRunnersAsHosted
  batch_class_name         | PrimaryKeyBatchingStrategy 
  table_name               | ci_runners                 
  column_name              | id                         
  job_arguments            | []                         
  total_tuple_count        |                            
  pause_ms                 | 100                        
  max_batch_size           |                            
  started_at               | 2025-05-06 22:40:08 UTC    
  on_hold_until            |                            
  gitlab_schema            | gitlab_ci                  
  finished_at              | 2025-05-06 22:40:13 UTC    
  queued_migration_version | 20250505095336             
  min_cursor               |                            
  max_cursor               |                            

• gitlab:background_migrations:pause[id]

• gitlab:background_migrations:resume[id]

References

• Batched background migrations CLI (&16479)

Screenshots or screen recordings

Before	After

How to set up and validate locally

MR acceptance checklist

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