Update repository, seed and service layers

WebAPI/Infrastructure/DefaultSqlConnectionFactory.cs

@@ -0,0 +1,25 @@
+using DataAccessLayer.Sql;
+using Microsoft.Data.SqlClient;
+
+namespace WebAPI.Infrastructure
+{
+    public class DefaultSqlConnectionFactory : ISqlConnectionFactory
+    {
+        private readonly string _connectionString;
+
+        public DefaultSqlConnectionFactory(IConfiguration configuration)
+        {
+            _connectionString =
+                Environment.GetEnvironmentVariable("DB_CONNECTION_STRING")
+                ?? configuration.GetConnectionString("Default")
+                ?? throw new InvalidOperationException(
+                    "Database connection string not configured. Set DB_CONNECTION_STRING env var or ConnectionStrings:Default."
+                );
+        }
+
+        public SqlConnection CreateConnection()
+        {
+            return new SqlConnection(_connectionString);
+        }
+    }
+}