Cannot pause form on a step with a date filled in (not yet saved)

[LaurensBurger]

Product versie / Product version

2.7.x - 2.8.1

Customer reference

Gron 46

Omschrijf het probleem / Describe the bug

{
    "type": "openforms.nl/fouten/ValidationError/",
    "code": "invalid",
    "title": "Invalid input.",
    "status": 400,
    "detail": "",
    "instance": "urn:uuid:8101799f-8da2-4b54-a99a-b82d9dad2bc4",
    "invalidParams": [
        {
            "name": "data.datum",
            "code": "invalid",
            "reason": "Date heeft het verkeerde formaat, gebruik 1 van deze formaten: YYYY-MM-DD."
        }
    ]
}

Does not happen when the date was previously saved by navigating to the next step and does not occur with datetime components.

[joeribekker]

Refinement: Probably a localization issue, where FormIO submit is not run before backend save? BUT we also DONT want to run FormIO submit because it will run validation on the entire form step - which is exactly what we want to bypass.

Might be worth looking into formio formatting for serialization?