Refactor data layer, add business layer

DataLayer/scripts/seed/procedures/USP_AddUserCredentials.sql

@@ -0,0 +1,20 @@
+CREATE OR ALTER PROCEDURE dbo.USP_AddUserCredentials
+(
+    @Hash dbo.TblUserHashes READONLY
+)
+AS
+BEGIN
+    SET NOCOUNT ON;
+    SET XACT_ABORT ON;
+
+    BEGIN TRANSACTION;
+
+    INSERT INTO dbo.UserCredential
+        (UserAccountId, Hash)
+    SELECT
+        uah.UserAccountId,
+        uah.Hash
+    FROM @Hash AS uah;
+
+    COMMIT TRANSACTION;
+END;