Alberta base personal credit

Fixes #376

policyengine_canada/parameters/gov/provinces/ab/tax/income/credits/base.yaml

@@ -0,0 +1,10 @@
+description: Alberta provides this maximum amount under the personal credit. 
+values:
+  2023-01-01: 21_003
+metadata:
+  unit: currency-CAD
+  period: year
+  label: Alberta base personal credit maximum amount
+  reference:
+  - title: Alberta income tax personal credit
+    href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/td1ab/td1ab-23e.pdf

policyengine_canada/tests/gov/provinces/ab/tax/income/credits/base.yaml

@@ -0,0 +1,6 @@
+- name: Alberta Base
+  period: 2023
+  input:
+    province_code: AB
+  output:
+    ab_base_personal_credit: 21_003

policyengine_canada/variables/gov/provinces/ab/tax/income/credits/ab_base_personal_credit.py

@@ -0,0 +1,15 @@
+from policyengine_canada.model_api import *
+
+
+class ab_base_personal_credit(Variable):
+    value_type = float
+    entity = Person
+    label = "Alberta base personal credit"
+    unit = CAD
+    definition_period = YEAR
+    reference = "https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/td1ab/td1ab-23e.pdf"
+    defined_for = ProvinceCode.AB
+
+    def formula(person, period, parameters):
+        base = parameters(period).gov.provinces.ab.tax.income.credits.base
+        return p