Add itemProperties to all CatalogGroups

[nf-s]

itemProperties should be available for all CatalogGroups

[wibily]

nick: should be done at groupMixin level unless too hard

[wibily]

this property exists on a few random groups, figure out a way to make this sane

[wibily]

nanda: group can have different items and need to ensure that traits are applicable to all of htem

[tephenavies]

I've read through a lot of groups and my thoughts so far are:

Groups that implement itemProperties (mostly?) do it by setting properties from itemProperties on the underride stratum:

terriajs/lib/Models/Catalog/Esri/ArcGisMapServerCatalogGroup.ts

Lines 253 to 267 in b359a16

	// Replace the stratum inherited from the parent group.
	const stratum = CommonStrata.underride;
	model.strata.delete(stratum);
	model.setTrait(stratum, "name", replaceUnderscores(layer.name));
	var uri = new URI(this._catalogGroup.url).segment(layer.id + ""); // Convert layer id to string as segment(0) means sthg different.
	model.setTrait(stratum, "url", uri.toString());
	if (this._catalogGroup.itemProperties !== undefined) {
	Object.keys(this._catalogGroup.itemProperties).map((k: any) =>
	model.setTrait(stratum, k, this._catalogGroup.itemProperties![k])
	);
	}

This works well on a per-group basis, but is hard to port to a Mixin (because each group sets not only the properties from itemProperties, but also additional properties that need to be passed down - note name & url above). Deleting and setting the underride stratum in GroupMixin as well as in the group would result in one of them being destructive to the other.

Thoughts/ideas:

• Have a new stratum for itemProperties separate to underride for other properties that are passed down
• I'll have to pass only properties that match the model down, or avoid errors with passing down non-matching properties

This is interesting, potentially useful for creating an itemProperties stratum:

terriajs/lib/Models/Catalog/Ckan/CkanCatalogGroup.ts

Lines 27 to 48 in f809727

	export function createInheritedCkanSharedTraitsStratum(
	model: Model<CkanSharedTraits>
	): Readonly<StratumFromTraits<CkanSharedTraits>> {
	const propertyNames = Object.keys(CkanSharedTraits.traits);
	const reduced: any = propertyNames.reduce(
	(p, c) => ({
	...p,
	get [c]() {
	return (model as any)[c];
	}
	}),
	{}
	);
	return observable(reduced);
	}
	createInheritedCkanSharedTraitsStratum.stratumName =
	"ckanItemReferenceInheritedPropertiesStratum";
	StratumOrder.addDefinitionStratum(
	createInheritedCkanSharedTraitsStratum.stratumName
	);

[nf-s]

Closed by #6218