[PM-13999] Show estimated tax for taxable countries (#5077)

src/Core/Billing/Services/ITaxService.cs

@@ -0,0 +1,22 @@
+namespace Bit.Core.Billing.Services;
+
+public interface ITaxService
+{
+    /// <summary>
+    /// Retrieves the Stripe tax code for a given country and tax ID.
+    /// </summary>
+    /// <param name="country"></param>
+    /// <param name="taxId"></param>
+    /// <returns>
+    /// Returns the Stripe tax code if the tax ID is valid for the country.
+    /// Returns null if the tax ID is invalid or the country is not supported.
+    /// </returns>
+    string GetStripeTaxCode(string country, string taxId);
+
+    /// <summary>
+    /// Returns true or false whether charging or storing tax is supported for the given country.
+    /// </summary>
+    /// <param name="country"></param>
+    /// <returns></returns>
+    bool IsSupported(string country);
+}