Table constraint creates a new index

Interesting, this gives me

[5] pry(main)> indexes.extra_indexes
=> ["iteration_start_and_due_date_iterations_cadence_id_constraint", "sequence_is_unique_per_iterations_cadence_id", "inc_mgmnt_no_overlapping_oncall_shifts"]

All these indexes I can see in my local database, but they are defined as constraints in structure.sql, for example

ALTER TABLE ONLY incident_management_oncall_shifts
    ADD CONSTRAINT inc_mgmnt_no_overlapping_oncall_shifts EXCLUDE USING gist (rotation_id WITH =, tstzrange(starts_at, ends_at, '[)'::text) WITH &&);

Not sure what we can do about this. 🤔

By @krasio.

More context here: !110637 (comment 1267723155)