Max safe integer not compatible with graphql type

[chladog]

Describe the bug
in getSaleableStockLevel method there is this piece of code:

        const inventoryNotTracked =
            variant.trackInventory === GlobalFlag.FALSE ||
            (variant.trackInventory === GlobalFlag.INHERIT && trackInventory === false);
        if (inventoryNotTracked) {
            return Number.MAX_SAFE_INTEGER;
        }

Which returns max JS safe integer, however that is not compatible with GraphlQLs "Int" type. (Int cannot represent non 32-bit signed integer value: 9007199254740991)

Expected behavior
Max number possible for GraphQL Int type.

Environment (please complete the following information):

• @vendure/core version: v0.18.4

[michaelbromley]

Is the graphql error occurring in one of the default API operations? Or are you using that method in a custom operation?

[chladog]

I used this method for custom "saleable" resolver.

[michaelbromley]

I considered changing it to:

return 2 ** 31 -1; // max 32-bit signed int, so it is safe for the GraphQL Int type

but I decided against it because I don't want the GraphQL abstraction leaking into a service method like that. Since you control the resolver, it's trivial to add a Math.min() around the result to make it safe for GraphQL.

On a related note, I've just implemented a solution to #442 which will allow you to specify a StockDisplayStrategy which you may find preferable to use in future.