Add Datadog integration (#6289)

* Event integration updates and cleanups

* Add Datadog integration

* Update README to include link to Datadog PR

* Move doc update into the Datadog PR; Fix empty message on ArgumentException

* Adjust exception message

Co-authored-by: Matt Bishop <mbishop@bitwarden.com>

* Removed unnecessary nullable enable; Moved Docs link to PR into this PR

* Remove unnecessary nullable enable calls

---------

Co-authored-by: Matt Bishop <mbishop@bitwarden.com>

src/Core/AdminConsole/Enums/IntegrationType.cs

@@ -6,7 +6,8 @@ public enum IntegrationType : int
     Scim = 2,
     Slack = 3,
     Webhook = 4,
-    Hec = 5
+    Hec = 5,
+    Datadog = 6
 }
 
 public static class IntegrationTypeExtensions
@@ -21,6 +22,8 @@ public static class IntegrationTypeExtensions
                 return "webhook";
             case IntegrationType.Hec:
                 return "hec";
+            case IntegrationType.Datadog:
+                return "datadog";
             default:
                 throw new ArgumentOutOfRangeException(nameof(type), $"Unsupported integration type: {type}");
         }