Implemented tax collection for subscriptions (#1017)

* Implemented tax collection for subscriptions

* Cleanup for Sales Tax

* Cleanup for Sales Tax

* Changes a constraint to an index for checking purposes

* Added and implemented a ReadById method for TaxRate

* Code review fixes for Tax Rate implementation

* Code review fixes for Tax Rate implementation

* Made the SalesTax migration script rerunnable

src/Sql/dbo/Stored Procedures/TaxRate_Create.sql

@@ -0,0 +1,30 @@
+CREATE PROCEDURE [dbo].[TaxRate_Create]
+    @Id VARCHAR(40),
+    @Country VARCHAR(50),
+    @State VARCHAR(2),
+    @PostalCode VARCHAR(10),
+    @Rate DECIMAL(5,2),
+    @Active BIT
+AS
+BEGIN
+    SET NOCOUNT ON
+
+    INSERT INTO [dbo].[TaxRate]
+    (
+        [Id],
+        [Country],
+        [State],
+        [PostalCode],
+        [Rate],
+        [Active]
+    )
+    VALUES
+    (
+        @Id,
+        @Country,
+        @State,
+        @PostalCode,
+        @Rate,
+        1
+    )
+END