Add the Connecticut EITC to the list of refundable credits

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+    - Add the Connecticut EITC to the list of refundable credits.

policyengine_us/parameters/gov/states/ct/tax/income/credits/refundable.yaml

@@ -0,0 +1,9 @@
+description: Connecticut provides the following refundable tax credits.
+metadata:
+  unit: list
+  period: year
+  label: Connecticut refundable credits
+
+values:
+  2021-01-01:
+    - ct_eitc

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

@@ -25,3 +25,32 @@
         state_fips: 9  # CT
   output:  # expected results from patched TAXSIM35 2024-03-07 version
     ct_income_tax: 404
+
+- name: Tax unit with taxsimid 99900 in p21.its.csv and p21.ots.csv
+  absolute_error_margin: 0.01
+  period: 2021
+  input:
+    people:
+      person1:
+        age: 68
+        employment_income: 16_010
+      person2:
+        age: 11
+      person3:
+        age: 11
+      person4:
+        age: 16
+    tax_units:
+      tax_unit:
+        members: [person1, person2, person3, person4]
+        premium_tax_credit: 0  # not in TAXSIM35
+    spm_units:
+      spm_unit:
+        members: [person1, person2, person3, person4]
+        snap: 0  # not in TAXSIM35
+    households:
+      household:
+        members: [person1, person2, person3, person4]
+        state_fips: 9  # CT
+  output:  # expected results from patched TAXSIM35 2024-03-17 version
+    ct_income_tax: -2_052.04

policyengine_us/variables/gov/states/ct/tax/income/ct_refundable_credits.py

@@ -8,3 +8,5 @@ class ct_refundable_credits(Variable):
     unit = USD
     definition_period = YEAR
     defined_for = StateCode.CT
+
+    adds = "gov.states.ct.tax.income.credits.refundable"