Format datetime fields in API as ISO8601

[timobrembeck]

Motivation

When implementing the API, we replicated the WordPress API as similar as possible, including some weird date formats which are not ideal for processing them in the apps.

Proposed Solution

• For every datetime field, add a new field to represent the same date in ISO_8601 format. This affects e.g.:
  • The start_date, start_time/ end_date, end_time fields of events - combine them into start/end
  • The sent_date field of push notifications
  • The modified_gmt field of all other objects (maybe also rename this to last_updated or last_modified)

Alternatives

Additional Context

[steffenkleinle]

Could we perhaps move this a little bit up please? We still have to live with moment and the date formatting workaround :/ Only if it fits in though, not super urgent, the current state continues to work.

[svenseeberg]

Should be possible, yes :)

[JanErikHuehne]

Is it correct, that the sent_date and modified_gmt have already been modified beforehand?

[timobrembeck]

Is it correct, that the sent_date and modified_gmt have already been modified beforehand?

The modified_gmt field of pages & imprint is already correct, but e.g. the modified_gmt field of the event and location API reponse and the timestamp field of the push notification API are in the Y-m-d H:i:s format, but the desired format is YYYY-MM-DDTHH:MM:SS.fff - the representation of datetime.isoformat() (which is also the default string representation of a DateTimeField in Django, so just use the unformatted - but timezone aware - model field in the API response and Django will automatically format it correctly).