Other metadata sources such as ThePornDB and timestamp.trade support end times for markers but Stash did not yet support saving those. This is a first step which only allows end time to be set either via API or via UI. Other aspects of Stash such as video player timeline are not yet updated to take end time into account.

- User can set end time when creating or editing markers in the UI or in the API.
- End time cannot be before start time. This is validated in the backend and for better UX also in the frontend.
- End time is shown in scene details view or markers wall view if present.
- Existing markers in the database will be updated to have -1 for end.
- GraphQL API does not require end_seconds. Omitted end_seconds will default to -1.

- 'seconds' is the required start time of a marker (in seconds).
- 'end_seconds' is an optional end time of a marker (in seconds).

Both fields support decimals.

Using -1 as a null value isn't really ideal.