Markers API `updated_at` property does not include timezone

Environment

• Pleroma version (could be found in the "Version" tab of settings in Pleroma-FE): Discovered in rebelbase.site which reports the version as "2.7.2 (compatible; Pleroma 2.6.0)"

Bug description

The markers API response from a Pleroma 2.6 server returns the updated_at property as an ISO8601 date/time (per the code in https://git.pleroma.social/pleroma/pleroma/-/blob/develop/lib/pleroma/web/mastodon_api/views/marker_view.ex) without a timezone.

E.g.,

{
    "notifications": {
        "last_read_id": "",
        "pleroma": {
            "unread_count": 1
        },
    "updated_at": "2024-03-24T14:01:35",
    "version": 0
    }
}

I suspect (but have not verified) that changing this line:

updated_at: NaiveDateTime.to_iso8601(m.updated_at),

in the code to:

updated_at: Utils.to_masto_date(m.updated_at),

will fix this.

Reported via gvansanden who discovered this in https://github.com/pachli/pachli-android/issues/562