ESS Source metadata writing helper.

[YooSunYoung]

Continued from scipp/essnmx#187 (comment)

@jl-wynen Did you mean omething like this...?

[jl-wynen]

No, I meant to add this in ScippNeutron. We already have a model there: https://github.com/scipp/scippneutron/blob/2e0e19fa73dc9b8f131f0a770740a56c899e723d/src/scippneutron/metadata/_model.py#L362 But we don't have any methods for writing to nexus yet. Writing is done by a couple of different sub packages. E.g., https://github.com/scipp/scippneutron/blob/2e0e19fa73dc9b8f131f0a770740a56c899e723d/src/scippneutron/io/cif.py#L268 I didn't want to bloat the model definition with all sorts of writers. Plus, the formats and how they mix models can vary a lot. But since we have nexus loaders in _model.py, we could probably add writers, too.

[YooSunYoung]

No, I meant to add this in ScippNeutron. We already have a model there: https://github.com/scipp/scippneutron/blob/2e0e19fa73dc9b8f131f0a770740a56c899e723d/src/scippneutron/metadata/_model.py#L362 But we don't have any methods for writing to nexus yet. Writing is done by a couple of different sub packages. E.g., https://github.com/scipp/scippneutron/blob/2e0e19fa73dc9b8f131f0a770740a56c899e723d/src/scippneutron/io/cif.py#L268 I didn't want to bloat the model definition with all sorts of writers. Plus, the formats and how they mix models can vary a lot. But since we have nexus loaders in _model.py, we could probably add writers, too.

I see. 🌚... I'll move this to scippneutron then.