Add stage_name to ci_finished_builds ClickHouse table

What does this MR do and why?

Add stage_name to ci_finished_builds ClickHouse table

References

#580441 (comment 2959137261)

How to set up and validate locally

• Start ClickHouse locally

gdk start clickhouse

• Apply the migration

bundle exec rake gitlab:clickhouse:migrate

• Verify the schema changes
  • Connect to your local ClickHouse instance:

clickhouse-client --host=localhost --port=9000 --user=default

• Check that the 'stage_name' column is added to the tables:

DESCRIBE TABLE ci_finished_builds;

• To Rollback the migration:

bin/rails gitlab:db:clickhouse:rollback

MR acceptance checklist

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