fix: [SFCC-471] Changed the default value of Algolia_InStockThreshold to 1, additional related fixes

[ede-somogyi-algolia]

Issue description

Setting the value of the Algolia_InStockThreshold site preference to 0 (the current default) breaks in_stock calculation.

The default value was changed from no value to 0 in #110 .

When setting up a new cartridge installation, a default value of 0 leads to all products always returning in_stock == true.

Context: SFCC didn’t require a default to be set before – the code treated leaving it empty as if there was no limit set and handled it correctly (i.e. didn’t take the value of this preference into account at all, falling back to the expected behavior of “treat a product as in-stock if it has at least 1 product in stock”).

The documentation shows this value as set to 1, which results in correct behavior.

#110 introduced an explicit 0 as the default value of this preference, which leads to problems due to the code returning in_stock === true if the product has at least 0 products in stock, so it always returns true for all products, which is erroneous behavior. Existing cartridge installations where there was no default value set should not encounter problems, but new installations will as all products will always return in_stock === true. To solve this, the logic was changed so that an ATS of 0 will never return true, no matter what value the Algolia_InStockThreshold preference is set to. This also guards against user error as the user can set 0 as the InStockThreshold, even if that’s not the default.

Changes in this PR

• changed the default value of Algolia_InStockThreshold to 1 so new installations will now set this value
• isInStock() in productFilter.js now returns true only if ATS > 0
• when none of the variants are in stock, the isInStock() method didn't previously return anything, fixed
• isInStoreStock() in productFilter.js now returns true only if ATS > 0
• isCustomVariationGroupInStock() in productFilter.js now returns true only if ATS > 0
• storeAvailability() in algoliaLocalizedProduct.js now returns true only if ATS > 0
• productFilterConfig.example.js now shows the correct default of 1
• made the description of the Algolia_InStockThreshold site preference more explicit

[sbellone]

Thanks 👍
There is a lint issue to fix, and please target develop as this is an independent fix.

[sbellone]

Suggested change

	let inStock = productFilter.isInStock(product, ALGOLIA_IN_STOCK_THRESHOLD);
	if (!inStock && !INDEX_OUT_OF_STOCK) {
	return undefined;
	}
	return inStock;
	return productFilter.isInStock(product, ALGOLIA_IN_STOCK_THRESHOLD);

[ede-somogyi-algolia]

Closing pull request, re-opened in #248, pointing to develop