Partitioning: Add foreign key and secondary indexes to partitioned web_hook_logs

The third step for partitioning the web_hook_logs table (&5558 (closed)) is to add the foreign key and the secondary indexes defined for web_hook_logs to the partitioned table.

Foreign key to be added:

• fk_rails_666826e111 FOREIGN KEY (web_hook_id) REFERENCES web_hooks(id) ON DELETE CASCADE

Indexes to be added:

• index_web_hook_logs_on_created_at_and_web_hook_id btree (created_at, web_hook_id)
• index_web_hook_logs_on_web_hook_id btree (web_hook_id)

It has to follow the cleanup and successful completion of the backfilling migration (#323675 (closed)) and will be deployed in the same milestone as that operation.