Fix Delaware itemized deductions logic

Fixes #4362

policyengine_us/tests/policy/baseline/gov/states/de/tax/income/integration.yaml

@@ -226,3 +226,68 @@
         state_fips: 10  # DE
   output:  # expected results from patched TAXSIM35 2024-04-04 version
     de_income_tax: 2429.20
+
+- name: Tax unit with taxsimid 6600 in k21.its.csv and k21.ots.csv
+  absolute_error_margin: 0.01
+  period: 2021
+  input:
+    people:
+      person1:
+        age: 73
+        employment_income: 20010
+        qualified_dividend_income: 1005.0
+        taxable_interest_income: 5505.0
+        short_term_capital_gains: 2005.0
+        long_term_capital_gains: 4005.0
+        rental_income: 505.0
+        taxable_private_pension_income: 3000.0
+        social_security_retirement: 6000.0
+        real_estate_taxes: 1000
+        mortgage_interest: 31000
+        self_employment_income: 137010
+        business_is_qualified: true
+        business_is_sstb: false
+        w2_wages_from_qualified_business: 100e6
+        ssi: 0  # not in TAXSIM35
+        state_supplement: 0  # not in TAXSIM35
+        wic: 0  # not in TAXSIM35
+        ma_covid_19_essential_employee_premium_pay_program: 0  # not in TAXSIM35
+      person2:
+        age: 73
+        employment_income: 12010
+        qualified_dividend_income: 1005.0
+        taxable_interest_income: 5505.0
+        short_term_capital_gains: 2005.0
+        long_term_capital_gains: 4005.0
+        rental_income: 505.0
+        taxable_private_pension_income: 3000.0
+        social_security_retirement: 6000.0
+        ssi: 0  # not in TAXSIM35
+        state_supplement: 0  # not in TAXSIM35
+        wic: 0  # not in TAXSIM35
+        ma_covid_19_essential_employee_premium_pay_program: 0  # not in TAXSIM35
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+        local_income_tax: 0  # not in TAXSIM35
+        state_sales_tax: 0  # not in TAXSIM35
+        ca_use_tax: 0  # not in TAXSIM35
+        il_use_tax: 0  # not in TAXSIM35
+        nm_2021_income_rebate: 0  # not in TAXSIM35
+        nm_additional_2021_income_rebate: 0  # not in TAXSIM35
+        nm_supplemental_2021_income_rebate: 0  # not in TAXSIM35
+        ny_supplemental_eitc: 0  # not in TAXSIM35
+        ok_use_tax: 0  # not in TAXSIM35
+        pa_use_tax: 0  # not in TAXSIM35
+        vt_renter_credit: 0  # not in TAXSIM35
+    spm_units:
+      spm_unit:
+        members: [person1, person2]
+        snap: 0  # not in TAXSIM35
+        tanf: 0  # not in TAXSIM35
+    households:
+      household:
+        members: [person1, person2]
+        state_fips: 10  # DE
+  output:  # expected results from patched TAXSIM35 2024-04-09 version
+    de_income_tax: 7429.24

policyengine_us/variables/gov/states/de/tax/income/deductions/de_deduction_indv.py

@@ -11,6 +11,7 @@ class de_deduction_indv(Variable):
     defined_for = StateCode.DE
 
     def formula(person, period, parameters):
+        itemizes = person.tax_unit("de_tax_unit_itemizes", period)
         itemized = person("de_itemized_deductions_indv", period)
         standard = person("de_standard_deduction_indv", period)
-        return max_(itemized, standard)
+        return where(itemizes, itemized, standard)

policyengine_us/variables/gov/states/de/tax/income/deductions/de_tax_unit_itemizes.py

@@ -0,0 +1,14 @@
+from policyengine_us.model_api import *
+
+
+class de_tax_unit_itemizes(Variable):
+    value_type = bool
+    entity = TaxUnit
+    label = "Whether the tax unit in Delaware itemizes the deductions when married filing separately"
+    definition_period = YEAR
+    defined_for = StateCode.MT
+
+    def formula(tax_unit, period, parameters):
+        itemized_ded = add(tax_unit, period, ["de_itemized_deductions_indiv"])
+        standard_ded = add(tax_unit, period, ["de_standard_deduction_indiv"])
+        return itemized_ded > standard_ded