Sanitize existing TODOs for confidential notes

# info about deleted todos is logged in application_json.log:
{"severity":"INFO","time":"2022-06-03T07:00:57.163Z","correlation_id":null,"message":"SanitizeConfidentialNoteTodos deleting invalid todo","attributes":{"id":15,"user_id":14,"project_id":8,"target_id":495,"target_type":"Issue","author_id":14,"action":4,"state":"pending","created_at":"2022-06-03T07:00:37.891Z","updated_at":"2022-06-03T07:00:37.891Z","note_id":1492,"commit_id":null,"group_id":null,"resolved_by_action":null}}

# no standard output:
$ bin/rails db:migrate
main: == 20220601145406 SanitizeConfidentialNoteTodos: migrating ====================
main: == 20220601145406 SanitizeConfidentialNoteTodos: migrated (2.5112s) ===========

$ bin/rails db:rollback:main
main: == 20220601145406 SanitizeConfidentialNoteTodos: reverting ====================
main: == 20220601145406 SanitizeConfidentialNoteTodos: reverted (0.0004s) ===========

explain SELECT "notes"."id" FROM "notes" WHERE "notes"."confidential" = true AND "notes"."id" > 100 ORDER BY "notes"."id" ASC LIMIT 100;

 Limit  (cost=0.28..5.41 rows=100 width=4) (actual time=4.225..124.491 rows=100 loops=1)
   Buffers: shared hit=54 read=27
   I/O Timings: read=123.783 write=0.000
   ->  Index Only Scan using index_notes_on_id_where_confidential on public.notes  (cost=0.28..300.62 rows=5852 width=4) (actual time=4.221..124.442 rows=100 loops=1)
         Index Cond: (notes.id > 100)
         Heap Fetches: 3
         Buffers: shared hit=54 read=27
         I/O Timings: read=123.783 write=0.000


Getting Todos for a batch of notes would look like this:

explain SELECT "todos".* FROM "todos" WHERE "todos"."note_id" IN (SELECT "notes"."id" FROM "notes" WHERE "notes"."confidential" = true AND "notes"."id" > 100 ORDER BY "notes"."id" ASC LIMIT 100);

 Nested Loop  (cost=7.23..440.37 rows=311 width=107) (actual time=0.501..0.502 rows=0 loops=1)
   Buffers: shared hit=481
   I/O Timings: read=0.000 write=0.000
   ->  HashAggregate  (cost=6.66..7.66 rows=100 width=4) (actual time=0.243..0.262 rows=100 loops=1)
         Group Key: notes.id
         Buffers: shared hit=81
         I/O Timings: read=0.000 write=0.000
         ->  Limit  (cost=0.28..5.41 rows=100 width=4) (actual time=0.056..0.208 rows=100 loops=1)
               Buffers: shared hit=81
               I/O Timings: read=0.000 write=0.000
               ->  Index Only Scan using index_notes_on_id_where_confidential on public.notes  (cost=0.28..300.62 rows=5852 width=4) (actual time=0.054..0.191 rows=100 loops=1)
                     Index Cond: (notes.id > 100)
                     Heap Fetches: 3
                     Buffers: shared hit=81
                     I/O Timings: read=0.000 write=0.000
   ->  Index Scan using index_todos_on_note_id on public.todos  (cost=0.57..4.30 rows=3 width=107) (actual time=0.002..0.002 rows=0 loops=100)
         Index Cond: (todos.note_id = notes.id)
         Buffers: shared hit=400
         I/O Timings: read=0.000 write=0.000