Wrap up CI partition management

Ref: #454978 (closed)

What does this MR do and why?

This MR hooks up the last pieces together in order to introduce our CI partition automation framework.

Once we will enable our feature flag , this will create a new ci_partition record and the associated database partitions for CI models if one given partition > 100 GB.

It will then switch the writes to this new partition when everything has been provisioned correctly.

This feature is behind a feature flag ci_partitioning_automation.

How to test this locally?

1. Tweak Ci::Partition::MAX_PARTITION_SIZE = 1.byte
2. Enable those 3 FF
  * Feature.enable(:ci_current_partition_value_102) # used to set up the current partition correctly
  * Feature.enable(:ci_partitioning_first_records) # used to populate the first records
  * Feature.enable(:ci_partitioning_automation) # used to create ci_partition dynamically
3. Run those 2 workers to simulate how the system will work on production
  * Ci::PartitioningWorker.new.perform # this is executed once a day
  * Gitlab::Database::Partitioning.sync_partitions # this is executed 4 times a day

How verify this locally?

1. Ci::Partition.all
2. Verify all new records are being created and updated successfully

• https://gitlab.com/gitlab-org/gitlab/-/blob/6f1d33cd7e03c79f20146f93120b3a94d3bc8552/config/initializers/postgres_partitioning.rb#L13-23

gdk psql -d gitlabhq_development_ci

Verify all Ci partitioned tables have new partitions created successfully
\d+ p_ci_pipelines_variables
\d+ p_ci_builds_names
...