feat(tax): normalize country and province code (#6513)

**What**
- Ensures that country and province codes are always stored as lower case.
- Ensures that calculation context normalizes input before getting region rates.

packages/tax/integration-tests/__tests__/index.spec.ts

@@ -34,14 +34,14 @@ moduleIntegrationTestRunner({
           expect.arrayContaining([
             expect.objectContaining({
               id: region.id,
-              country_code: "US",
+              country_code: "us",
               province_code: null,
               parent_id: null,
             }),
             expect.objectContaining({
               id: provinceRegion.id,
-              country_code: "US",
-              province_code: "CA",
+              country_code: "us",
+              province_code: "ca",
               parent_id: region.id,
             }),
           ])
@@ -397,6 +397,7 @@ moduleIntegrationTestRunner({
         expect(taxRegions).toEqual([
           expect.objectContaining({
             id: region.id,
+            country_code: "us",
             deleted_at: expect.any(Date),
           }),
         ])

packages/tax/src/services/tax-module-service.ts

@@ -160,28 +160,10 @@ export default class TaxModuleService<
     data: TaxTypes.CreateTaxRegionDTO | TaxTypes.CreateTaxRegionDTO[],
     @MedusaContext() sharedContext: Context = {}
   ) {
-    const input = Array.isArray(data) ? data : [data]
-    await this.verifyProvinceToCountryMatch(input, sharedContext)
-    const [defaultRates, regionData] = input.reduce(
-      (acc, region) => {
-        const { default_tax_rate, ...rest } = region
-        if (!default_tax_rate) {
-          acc[0].push(null)
-        } else {
-          acc[0].push({
-            ...default_tax_rate,
-            is_default: true,
-            created_by: region.created_by,
-          })
-        }
-        acc[1].push(rest)
-        return acc
-      },
-      [[], []] as [
-        (Omit<TaxTypes.CreateTaxRateDTO, "tax_region_id"> | null)[],
-        Partial<TaxTypes.CreateTaxRegionDTO>[]
-      ]
-    )
+    const { defaultRates, regionData } =
+      this.prepareTaxRegionInputForCreate(data)
+
+    await this.verifyProvinceToCountryMatch(regionData, sharedContext)
 
     const regions = await this.taxRegionService_.create(
       regionData,
@@ -251,16 +233,18 @@ export default class TaxModuleService<
     calculationContext: TaxTypes.TaxCalculationContext,
     @MedusaContext() sharedContext: Context = {}
   ): Promise<(TaxTypes.ItemTaxLineDTO | TaxTypes.ShippingTaxLineDTO)[]> {
+    const normalizedContext =
+      this.normalizeTaxCalculationContext(calculationContext)
     const regions = await this.taxRegionService_.list(
       {
         $or: [
           {
-            country_code: calculationContext.address.country_code,
+            country_code: normalizedContext.address.country_code,
             province_code: null,
           },
           {
-            country_code: calculationContext.address.country_code,
-            province_code: calculationContext.address.province_code,
+            country_code: normalizedContext.address.country_code,
+            province_code: normalizedContext.address.province_code,
           },
         ],
       },
@@ -355,6 +339,56 @@ export default class TaxModuleService<
     return itemTaxLines
   }
 
+  private normalizeTaxCalculationContext(
+    context: TaxTypes.TaxCalculationContext
+  ): TaxTypes.TaxCalculationContext {
+    return {
+      ...context,
+      address: {
+        ...context.address,
+        country_code: this.normalizeRegionCodes(context.address.country_code),
+        province_code: context.address.province_code
+          ? this.normalizeRegionCodes(context.address.province_code)
+          : null,
+      },
+    }
+  }
+
+  private prepareTaxRegionInputForCreate(
+    data: TaxTypes.CreateTaxRegionDTO | TaxTypes.CreateTaxRegionDTO[]
+  ) {
+    const regionsWithDefaultRate = Array.isArray(data) ? data : [data]
+
+    const defaultRates: (Omit<
+      TaxTypes.CreateTaxRateDTO,
+      "tax_region_id"
+    > | null)[] = []
+    const regionData: TaxTypes.CreateTaxRegionDTO[] = []
+
+    for (const region of regionsWithDefaultRate) {
+      const { default_tax_rate, ...rest } = region
+      if (!default_tax_rate) {
+        defaultRates.push(null)
+      } else {
+        defaultRates.push({
+          ...default_tax_rate,
+          is_default: true,
+          created_by: region.created_by,
+        })
+      }
+
+      regionData.push({
+        ...rest,
+        province_code: rest.province_code
+          ? this.normalizeRegionCodes(rest.province_code)
+          : null,
+        country_code: this.normalizeRegionCodes(rest.country_code),
+      })
+    }
+
+    return { defaultRates, regionData }
+  }
+
   private async verifyProvinceToCountryMatch(
     regionsToVerify: TaxTypes.CreateTaxRegionDTO[],
     sharedContext: Context = {}
@@ -531,4 +565,8 @@ export default class TaxModuleService<
       (a, b) => (a as any).priority_score - (b as any).priority_score
     )
   }
+
+  private normalizeRegionCodes(code: string) {
+    return code.toLowerCase()
+  }
 }

packages/types/src/tax/mutations.ts

@@ -15,7 +15,7 @@ export interface CreateTaxRegionDTO {
   parent_id?: string | null
   metadata?: Record<string, unknown>
   created_by?: string
-  default_tax_rate: {
+  default_tax_rate?: {
     rate?: number | null
     code?: string | null
     name: string