Compute "seconds" field in Field API preSave() rather than in widget form to play nice with API-based consumers

✨ Allow setting Duration field by supplying a string or numeric value Needs review is a duplicate of this, but I feel like the solution there is better, so let's close this one.

Hi @DieterHolvoet
I checked your solution and I don't like it, also only maintainers of module can decide on closing issues on d.org.
The custom conversion from seconds to date interval looks like something we need to avoid.
Imagine you have selected "1 year 11 months 50 days", when converted to timestamp and back to interval it will be "2 years 0 months 20 days".
So that would break main core feature of module which is ability to select specific date interval.

Hi @dww
I have reviewed patch from #4 and fixed all the issues you wrote about and added test to check seconds value after both form update and regular entity save.
Please have a look

Automatically closed - issue fixed for 2 weeks with no activity.