Investigate missing index on auto-create foreign keys

[aeneasr]

The CRDB meta schema appears to ignore auto-generated indices used for foreign keys when the foreign key is part of the create table statement.

[aeneasr]

To reproduce

create_table("identity_recovery_tokens") {
  t.Column("id", "uuid", {primary: true})

  t.ForeignKey("selfservice_recovery_request_id", {"selfservice_recovery_requests": ["id"]}, {"on_delete": "cascade"})
}

and later

change_column("identity_recovery_tokens", "selfservice_recovery_flow_id", "uuid", {"null": true})