fix: Allocate tax loss to tax account head on early payment discount (#34287)

* fix: Taxes aren't discounted on early payment discount

- Deductions in payment entry must be split into income loss and tax loss
- Compute total discount in percentage, makes discounting different amounts proportionately easier

(cherry picked from commit 768c3a4927)

* fix: Recalculate difference amount after setting deductions

(cherry picked from commit 75ec0a0a85)

* fix: Set deductions in base currency

- Use field precision to get more accurate values

(cherry picked from commit dc2998f544)

* fix: Back update discounted amount in Invoice based on discount type

- Discount value was always trated as a percentage on back updation

(cherry picked from commit 2ae5834290)

* test: PE from SI with early payment discount amount & PE assertions in discount % test

(cherry picked from commit c217bb2018)

* fix: Set deduction amount in company currency on Doctype

- Even via JS, deductions amount is always in company currency
- Since there is nothing dynamic about this field, set it in the doctype spec itself
- fixed: Inconsistency between label currency and field currency formatted value

(cherry picked from commit 7f2e7badff)

* fix: Don't add to deductions if amount is 0

- misc: better docstring

(cherry picked from commit f02fc8acf0)

* fix: Paid amount must be discounted considering accounting currency

- Accounting is in the same currency if party currency and company currency is the same
- If accounting is in the same currency, paid and recvd amount is in the base currency
- Then, discount amount must also be in the base currency as it is deducted from paid amount
- Received amount must be in base currency if not multi currency
- cleanup: Deductions setting broken into smaller functions

(cherry picked from commit 761f68d7bf)

* fix: Multi-currency SI with base currency PE

- Return total discount loss in base currency
- Allocate payment based on terms: Set allocated amount in references table in base currency if accounting is in that currency
- Allocate payment based on terms: While back updating set paid amount (payment schedule) in transaction currency always
- minor: discount msgprint in correct currency

(cherry picked from commit b09c2381ca)

* test: Multi currency SI with multi-currency accounting and single currency accounting + Early payment discount

(cherry picked from commit 9abf0ef615)

# Conflicts:
#	erpnext/accounts/doctype/payment_entry/test_payment_entry.py

* fix: Handle rounding more gracefully

- Round off pending discount loss to avoid miniscule losses rounded to 0.0 that are added in deductions
- Use base amounts to calculate base losses instead of using conversion factor which increases rounding error
- Round of total base loss instead of individual income and tax losses to reduce rounding error
- Use default round off account for pending rounding loss in deductions

(cherry picked from commit caa1a3dccf)

* fix: Provision to apply early payment discount if payment is recorded late

- Party could have paid on time but payment is recorded late
- Prompt for reference date so that discount is applied while mapping
- Prompt only if discount in payment schedule of valid doctypes
- test: Reference date and impact on PE
- `make_payment_entry` (JS) must be able to access `this`

(cherry picked from commit d6d0163514)

# Conflicts:
#	erpnext/accounts/doctype/payment_entry/payment_entry.py
#	erpnext/accounts/doctype/purchase_invoice/purchase_invoice.js
#	erpnext/buying/doctype/purchase_order/purchase_order.js
#	erpnext/public/js/controllers/transaction.js

* feat: Make Tax loss booking optional

- Checkbox in Accounts Settings
- Apply checkbox in PE deductions setting logic
- Adjust tests

(cherry picked from commit 216a46bd66)

# Conflicts:
#	erpnext/accounts/doctype/accounts_settings/accounts_settings.json

* fix: Merge conflicts

* fix: 'Donation' does not have `company_currency` field

- Make sure check uses this field only for eligible documents

---------

Co-authored-by: marination <maricadsouza221197@gmail.com>

erpnext/public/js/controllers/transaction.js

@@ -1987,22 +1987,62 @@ erpnext.TransactionController = erpnext.taxes_and_totals.extend({
 		}
 	},
 
-	make_payment_entry: function() {
+	make_payment_entry() {
+		let via_journal_entry = this.frm.doc.__onload && this.frm.doc.__onload.make_payment_via_journal_entry;
+		if(this.has_discount_in_schedule() && !via_journal_entry) {
+			// If early payment discount is applied, ask user for reference date
+			this.prompt_user_for_reference_date();
+		} else {
+			this.make_mapped_payment_entry();
+		}
+	},
+
+	make_mapped_payment_entry(args) {
+		var me = this;
+		args = args || { "dt": this.frm.doc.doctype, "dn": this.frm.doc.name };
 		return frappe.call({
-			method: cur_frm.cscript.get_method_for_payment(),
-			args: {
-				"dt": cur_frm.doc.doctype,
-				"dn": cur_frm.doc.name
-			},
+			method: me.get_method_for_payment(),
+			args: args,
 			callback: function(r) {
 				var doclist = frappe.model.sync(r.message);
 				frappe.set_route("Form", doclist[0].doctype, doclist[0].name);
-				// cur_frm.refresh_fields()
 			}
 		});
 	},
 
-	make_quality_inspection: function () {
+	prompt_user_for_reference_date(){
+		var me = this;
+		frappe.prompt({
+			label: __("Cheque/Reference Date"),
+			fieldname: "reference_date",
+			fieldtype: "Date",
+			reqd: 1,
+		}, (values) => {
+			let args = {
+				"dt": me.frm.doc.doctype,
+				"dn": me.frm.doc.name,
+				"reference_date": values.reference_date
+			}
+			me.make_mapped_payment_entry(args);
+		},
+		__("Reference Date for Early Payment Discount"),
+		__("Continue")
+		);
+	},
+
+	has_discount_in_schedule() {
+		let is_eligible = in_list(
+			["Sales Order", "Sales Invoice", "Purchase Order", "Purchase Invoice"],
+			this.frm.doctype
+		);
+		let has_payment_schedule = this.frm.doc.payment_schedule && this.frm.doc.payment_schedule.length;
+		if(!is_eligible || !has_payment_schedule) return false;
+
+		let has_discount = this.frm.doc.payment_schedule.some(row => row.discount_date);
+		return has_discount;
+	},
+
+	make_quality_inspection() {
 		let data = [];
 		const fields = [
 			{