Instructions unclear: REST API Documentation

While making API-calls one can't easily see what format is needed for e.g. dates (like in due-date in cards)
But there are also more things that are unclear, here a (hope so) full list:

• Date format in entities (JSON) (new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ssZ"))
• Date format in Header (If-Modified-Since) (new SimpleDateFormat("E, dd MMM yyyy hh:mm:ss z", Locale.US))
• All endpoints: reqired fields in entities (JSON), e.g. user must be set when updating a card
• Examples of requests (JSON) (full, no null fields like due-date 😝 )
• Optional: Link to https://github.com/nextcloud/Android-SingleSignOn

For anyone working on a third-party-app this would be very helpful.

Thanks!

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Start by locating the REST API documentation and its endpoint descriptions. Use the issue's checklist to document entity and header date formats, required JSON fields, complete request examples without null fields, and optionally the Android-SingleSignOn link. Done means the requested guidance is covered across all endpoints.