Stock items creation not adjusted for multi vendor

[omairrazam]

We need to make 2 adjustments which I think were missed.

1. variant.rb
   method = create_stock_items
   issue = it loops on all stock locations which don't event belong to given vendor
   expected = only create stock items for respective vendor's stock location

2. stock_location.rb
   method = create_stock_items
   issue = it loops on all variants of all vendor's.
   expected = only create stock item for respective vendor variants.

Overrall Impact faced:

i faced serious performance issue as number of vendors and products increased on my platform and I was able to find this as reason.

[giugrilli]

Same here, huge impact on vendor creation, heroku goes timeout

[damianlegawiec]

@giugrilli @omairrazam this issue has been partially resolved in Spree 4.3 and Multi-Vendor 2.2. Further improvements will be done in Spree v5 which will include multi-vendor in Spree core.

[giugrilli]

@damianlegawiec In the meantime I ended up just now doing this as a workaround, overriding the create_stock_location method.

`
Spree::Vendor.class_eval do

private

def create_stock_location
stock_location = stock_locations.where(name: name, country: Spree::Country.default).first_or_initialize
stock_location.propagate_all_variants = false
stock_location.save
end

end
`

The creation finalises correctly and fast.
Is this in your opinion a viable solution for the moment?