Disable pipeline schedules when a user is blocked

What does this MR do?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/323341

Screenshots (strongly suggested)

Queries:

• Finding the first "ci_pipeline_schedules"."id" that needs to be updated:
  • cold cache: https://console.postgres.ai/shared/572d1d7e-9d55-49e8-9918-a7be86ccbbf5
  • warm cache: https://console.postgres.ai/shared/5e438b6f-614c-4d1f-a523-bf095bbc7d83
  • with new index: https://console.postgres.ai/shared/6deb5726-151d-46c8-8d0e-d72eed8890f6
• Finding the upper limit for each batch:
  • https://console.postgres.ai/shared/16e3b31f-de77-4ba3-bb6c-0d0f3f087365
  • with new index: https://console.postgres.ai/shared/b0aebd65-1e33-44da-99e1-512c1c5b27ee
• Executing the update:
  • https://console.postgres.ai/shared/a82b6a90-48bc-4574-9c10-871273467de0
  • with new index: https://console.postgres.ai/shared/c657f093-71f3-4638-8b98-31489b6e7adb

Migrations

Up

VERSION=20210312140029 bin/rails db:migrate:up
== 20210312140029 AddOwnerAndIdIndexOnActiveCiPipelineSchedules: migrating ====
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:ci_pipeline_schedules, [:owner_id, :id], {:where=>"active = TRUE", :name=>"index_ci_pipeline_schedules_on_owner_id_and_id_and_active", :algorithm=>:concurrently})
   -> 0.0026s
-- execute("SET statement_timeout TO 0")
   -> 0.0005s
-- add_index(:ci_pipeline_schedules, [:owner_id, :id], {:where=>"active = TRUE", :name=>"index_ci_pipeline_schedules_on_owner_id_and_id_and_active", :algorithm=>:concurrently})
   -> 0.0063s
-- execute("RESET ALL")
   -> 0.0005s
== 20210312140029 AddOwnerAndIdIndexOnActiveCiPipelineSchedules: migrated (0.0109s)

Timing: The query has been executed. Duration: 0.206 s - https://gitlab.slack.com/archives/CLJMDRD8C/p1615557981427200

Down

VERSION=20210312140029 bin/rails db:migrate:down
== 20210312140029 AddOwnerAndIdIndexOnActiveCiPipelineSchedules: reverting ====
-- transaction_open?()
   -> 0.0000s
-- indexes(:ci_pipeline_schedules)
   -> 0.0029s
-- execute("SET statement_timeout TO 0")
   -> 0.0005s
-- remove_index(:ci_pipeline_schedules, {:algorithm=>:concurrently, :name=>"index_ci_pipeline_schedules_on_owner_id_and_id_and_active"})
   -> 0.0034s
-- execute("RESET ALL")
   -> 0.0005s
== 20210312140029 AddOwnerAndIdIndexOnActiveCiPipelineSchedules: reverted (0.0082s)

Does this MR meet the acceptance criteria?

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