Cascade delayed project removal setting to parent namespace [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Closes #321724 (closed)

Makes the POC from #291082 (closed) and !51498 (closed) production ready.

This will add the cascading setting framework plus make it work for the first attribute - delayed_project_removal.

NOTE: Keeping MR as draft until %13.10 release date - this must not be included in %13.10.

Database

Migrate

== 20210308175224 ChangeNamespaceSettingsDelayedProjectRemovalNull: migrating =
-- change_column(:namespace_settings, :delayed_project_removal, :boolean, {:null=>true, :default=>nil})
   -> 0.0041s
== 20210308175224 ChangeNamespaceSettingsDelayedProjectRemovalNull: migrated (0.0042s)

== 20210308175225 AddLockDelayedProjectRemovalToNamespaceSettings: migrating ==
-- add_column(:namespace_settings, :lock_delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0042s
== 20210308175225 AddLockDelayedProjectRemovalToNamespaceSettings: migrated (0.0043s)

== 20210308175226 AddDelayedProjectRemovalToApplicationSettings: migrating ====
-- add_column(:application_settings, :delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0042s
== 20210308175226 AddDelayedProjectRemovalToApplicationSettings: migrated (0.0042s)

== 20210308175227 AddLockDelayedProjectRemovalToApplicationSettings: migrating
-- add_column(:application_settings, :lock_delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0040s
== 20210308175227 AddLockDelayedProjectRemovalToApplicationSettings: migrated (0.0040s)

Rollback

== 20210308175227 AddLockDelayedProjectRemovalToApplicationSettings: reverting
-- remove_column(:application_settings, :lock_delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0113s
== 20210308175227 AddLockDelayedProjectRemovalToApplicationSettings: reverted (0.0132s)

== 20210308175226 AddDelayedProjectRemovalToApplicationSettings: reverting ====
-- remove_column(:application_settings, :delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0038s
== 20210308175226 AddDelayedProjectRemovalToApplicationSettings: reverted (0.0039s)

== 20210308175225 AddLockDelayedProjectRemovalToNamespaceSettings: reverting ==
-- remove_column(:namespace_settings, :lock_delayed_project_removal, :boolean, {:default=>false, :null=>false})
   -> 0.0046s
== 20210308175225 AddLockDelayedProjectRemovalToNamespaceSettings: reverted (0.0047s)

== 20210308175224 ChangeNamespaceSettingsDelayedProjectRemovalNull: reverting =
-- change_column_default(:namespace_settings, :delayed_project_removal, false)
   -> 0.0058s
-- change_column_null(:namespace_settings, :delayed_project_removal, false, false)
   -> 0.0038s
== 20210308175224 ChangeNamespaceSettingsDelayedProjectRemovalNull: reverted (0.0098s)

SQL

NOTE: Cannot run explain on lock query because the columns don't yet exist.

SELECT "namespace_settings"."delayed_project_removal" FROM "namespace_settings" join unnest(ARRAY[108,109,110,111]) with ordinality t(namespace_id, ord) USING (namespace_id) WHERE (delayed_project_removal IS NOT NULL) ORDER BY t.ord LIMIT 1

Explain: https://explain.depesz.com/s/3SfpV

Limit  (cost=0.44..3.90 rows=1 width=9) (actual time=7.626..7.629 rows=1 loops=1)
   Buffers: shared read=4
   I/O Timings: read=7.548
   ->  Nested Loop  (cost=0.44..346.25 rows=100 width=9) (actual time=7.624..7.626 rows=1 loops=1)
         Buffers: shared read=4
         I/O Timings: read=7.548
         ->  Function Scan on unnest t  (cost=0.00..1.00 rows=100 width=12) (actual time=0.009..0.010 rows=1 loops=1)
         ->  Index Scan using namespace_settings_pkey on public.namespace_settings  (cost=0.43..3.45 rows=1 width=5) (actual time=7.610..7.610 rows=1 loops=1)
               Index Cond: (namespace_settings.namespace_id = t.namespace_id)
               Filter: (namespace_settings.delayed_project_removal IS NOT NULL)
               Rows Removed by Filter: 0
               Buffers: shared read=4
               I/O Timings: read=7.548

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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• Documentation (if required)
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• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
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