fix: Multicurrency invoices using subscription

[deepeshgarg007]

The user gets the following error on trying to create an invoice using subscription against a party having billing currency other than the company currency

Sets to test the pull request

1. Create a customer with billing currency other than company currency, Eg USD if company currency is INR

2. Create a subscription plan in party currency
   

3. Create a backdated subscription as per the following details
   

4. Click on the fetch subscription updates button on the top right and see if the invoice gets generated successfully
   

[codecov]

Codecov Report

Merging #28916 (6ab7530) into develop (2be62c2) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop   #28916   +/-   ##
========================================
  Coverage    55.57%   55.58%           
========================================
  Files         1126     1126           
  Lines        67199    67201    +2     
========================================
+ Hits         37349    37355    +6     
+ Misses       29850    29846    -4     

Impacted Files	Coverage Δ
...next/accounts/doctype/subscription/subscription.py	81.84% <100.00%> (+0.10%)	⬆️
...work_order_stock_report/work_order_stock_report.py	50.00% <0.00%> (-50.00%)	⬇️
erpnext/assets/doctype/asset/depreciation.py	84.93% <0.00%> (-2.74%)	⬇️
.../report/stock_projected_qty/stock_projected_qty.py	86.84% <0.00%> (-2.64%)	⬇️
...eport/production_analytics/production_analytics.py	69.51% <0.00%> (-1.22%)	⬇️
erpnext/portal/utils.py	28.98% <0.00%> (ø)
...ext/payroll/doctype/payroll_entry/payroll_entry.py	70.79% <0.00%> (ø)
...stock/doctype/purchase_receipt/purchase_receipt.py	90.64% <0.00%> (ø)
erpnext/stock/report/stock_ageing/stock_ageing.py	91.24% <0.00%> (+0.72%)	⬆️
erpnext/stock/reorder_item.py	76.06% <0.00%> (+0.85%)	⬆️
... and 7 more

[deepeshgarg007]

@Mergifyio backport version-13-hotfix

[mergify]

backport version-13-hotfix

✅ Backports have been created

• #28932 fix: Multicurrency invoices using subscription (backport #28916) has been created for branch version-13-hotfix

[vanesaotaduy]

@deepeshgarg007 this pr doesn't solve the issue Subscription currency #29036.
When you set up the subscription plan with company currency and choose a price list in another currency, for example, USD, the invoice doesn't convert the amount. It takes the price in USD as it was in the company currency. Let me show you an example on V13:

I created this subscription plan by setting up ARS currency for the plan and choosing a Price List in USD.

The price for this product is 300 USD for the list price selected on the plan.

When issuing the invoice, takes the price as 300 ARS, which is wrong, it should be converted at the exchange rate of 1175 ARS.

The correct amount should be 300 x 1175 = 352.500 ARS