feat: display tax break up on salary slip

[saurabh6790]

Provision to display income tax deduction on salary slip.

• Salary Structure Assignment

  • Selected Tax regime as New Tax Regime where there are no standard deductions
  • Not considering Tax Exemption Declaration as New Tax Regime is selected

• Income tax breakup on Salary Slip

Income Tax Deducted Till Date + Future Income Tax Deductions
9,583.33+1,05,416.67 = 1,15,000

• Total payable tax as per Income tax computation

Calculations / Formula

• Calculate CTC

ctc = ( 
	previous_taxable_earnings 
	+ current_structured_taxable_earnings 
	+ future_structured_taxable_earnings 
	+ current_additional_earnings 
	+ other_incomes 
	+ unclaimed_taxable_benefits 
	+ non_taxable_earnings
)

• Calculate non-taxable earnings

non_taxable_earnings = (
	prev_period_non_taxable_earnings
	+ current_period_non_taxable_earnings
	+ future_period_non_taxable_earnings
	+ non_taxable_additional_salary
)

• Calculate Income from other sources

income_from_other_sources = fetch details from `Employee Other Income` based on payroll period

• Total Earnings

total_earnings = ctc + income_from_other_sources

• Annual deductions before tax calculations

annual_deductions_before_tax_calculation =  (
	prev_period_exempted_amount 
	+ current_period_exempted_amount 
	+ future_period_exempted_amount
)

• Standard deductions

standard_tax_exemption_amount = based on the selected tax slab

• Tax exemption declaration

tax_exemption_declaration =  total_declared_exemption_amount + standard_tax_exemption_amount

• Annual taxable amount

annual_taxable_amount = total_earnings - (
	non_taxable_earnings
	+ deductions_before_tax_calculation
	+ tax_exemption_declaration
	+ standard_tax_exemption_amount
)

• Income tax deducted up-to the current month

tax_deducted_till_date = previous_total_paid_taxes + current_structured_tax_amount

• Future taxable amount

future_income_tax_deductions = total_structured_tax_amount - income_tax_deducted_till_date

Re-write queries

Re-write queries in frappe ORM format for Salary Slip DocType

[codecov-commenter]

Codecov Report

Merging #267 (86428d1) into develop (bcc4c17) will increase coverage by 0.32%.
The diff coverage is 93.17%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #267      +/-   ##
===========================================
+ Coverage    71.00%   71.33%   +0.32%     
===========================================
  Files          181      181              
  Lines         9195     9321     +126     
===========================================
+ Hits          6529     6649     +120     
- Misses        2666     2672       +6     

Impacted Files	Coverage Δ
hrms/payroll/doctype/salary_slip/salary_slip.py	87.69% <93.10%> (+0.44%)	⬆️
...s/payroll/doctype/payroll_period/payroll_period.py	90.38% <100.00%> (+4.11%)	⬆️
...t/employee_leave_balance/employee_leave_balance.py	94.82% <0.00%> (+0.23%)	⬆️
...ype/employee_other_income/employee_other_income.py	100.00% <0.00%> (+100.00%)	⬆️

[nabinhait]

@saurabh6790 Income Tax Breakup fields can be organised like below:

[saurabh6790]

@ruchamahabal fixed!

[saurabh6790]

@nabinhait Reorganised as per the suggestion

[ruchamahabal]

@saurabh6790 can you address the unresolved conversations about splitting functions?

[saurabh6790]

@ruchamahabal Added test case. PR is ready to merge