feat(domain): add BadRequestException for invalid request errors

src/core/DigitalData.MessagingService.Domain/Exceptions/BadRequestException.cs

@@ -0,0 +1,21 @@
+namespace DigitalData.MessagingService.Domain.Exceptions
+{
+    /// <summary>
+    /// Exception thrown when a requested entity is not found.
+    /// </summary>
+    public class BadRequestException : Exception
+    {
+        public BadRequestException(string entityName, object key) : base($"{entityName} with key '{key}' was not found.")
+        {
+        }
+
+        public BadRequestException(string message) : base(message)
+        {
+        }
+
+        public BadRequestException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
+}