fix: Avoid automatic customer creation on website user login

[marination]

Issue:

TLDR: When a website user logs in, if they are not a customer and if cart is enabled, a customer was automatically created

• This user could have been created for blogs, or for other purposes, and not e-commerce.
• This happens because: on login, hooks triggers an event that sets the cart count. For this it tries to fetch the current users shopping cart (cart quotation). If it cannot find a quotation it creates a new one against this user. While doing this, it creates a customer if non-existent.
• If a quotation is found then its items count becomes the cart count, else an empty quotation(cart) is initialised.
• If a logged in user has ever added anything to cart, they are made a customer in the backend. So if this user is not a customer, we don't need to refresh the cart at all, it will be empty or non-existent.

Fix:

• Setting of cart count (refreshing the cart count) must happen only if the user logging in is a valid customer in the system. Otherwise the user has no business with the cart.
• Changed check_customer_or_supplier to is_customer. If supplier we were exiting the function anyway so why return it.

To test:

• Create a new website user (do not use this user for e-commerce)
• login as this user
• Check if customer was auto created after login

[codecov]

Codecov Report

Merging #27914 (a780f78) into develop (401e22f) will decrease coverage by 0.03%.
The diff coverage is 12.50%.

@@             Coverage Diff             @@
##           develop   #27914      +/-   ##
===========================================
- Coverage    54.40%   54.37%   -0.04%     
===========================================
  Files         1254     1254              
  Lines        67717    67720       +3     
===========================================
- Hits         36840    36820      -20     
- Misses       30877    30900      +23     

Impacted Files	Coverage Δ
erpnext/shopping_cart/utils.py	32.14% <12.50%> (-3.58%)	⬇️
...tch_item_expiry_status/batch_item_expiry_status.py	69.81% <0.00%> (-24.53%)	⬇️
...wise_balance_history/batch_wise_balance_history.py	69.49% <0.00%> (-22.04%)	⬇️
...ctype/woocommerce_settings/woocommerce_settings.py	80.39% <0.00%> (-3.93%)	⬇️
erpnext/stock/reorder_item.py	74.57% <0.00%> (-3.39%)	⬇️
...ctype/accounting_dimension/accounting_dimension.py	64.34% <0.00%> (-1.56%)	⬇️
...e/period_closing_voucher/period_closing_voucher.py	88.23% <0.00%> (-1.48%)	⬇️
erpnext/portal/utils.py	30.00% <0.00%> (-1.43%)	⬇️
.../report/stock_projected_qty/stock_projected_qty.py	88.31% <0.00%> (-1.30%)	⬇️
erpnext/stock/stock_ledger.py	85.76% <0.00%> (-1.27%)	⬇️
... and 13 more

[marination]

Not sure what test to write here, it just refreshes cart count. test case is too specific.

Failing UI tests are unrelated

[marination]

@Mergifyio backport version-13-hotfix

[mergify]

Command backport version-13-hotfix: success

Backports have been created

• #27926 fix: Avoid automatic customer creation on website user login (backport #27914) has been created for branch version-13-hotfix

[rasos]

We need to test the B2C scenario: a new user registers as s/he wants to buy an item with the cart. So that user is immediately a customer.