feat(dynamic-secret): Added new options to username template

docs/documentation/platform/dynamic-secrets/mongo-db.mdx

@@ -66,13 +66,28 @@ Create a user with the required permission in your MongoDB instance. This user w
 	<ParamField path="CA(SSL)" type="string">
 		A CA may be required if your DB requires it for incoming connections.
 	</ParamField>
-  <ParamField path="Username Template" type="string" default="{{randomUsername}}">
+<ParamField path="Username Template" type="string" default="{{randomUsername}}">
     Specifies a template for generating usernames. This field allows customization of how usernames are automatically created.
 
     Allowed template variables are
     - `{{randomUsername}}`: Random username string
     - `{{unixTimestamp}}`: Current Unix timestamp
-	- `{{identityName}}`: Name of the identity that is generating the secret
+    - `{{identity.name}}`: Name of the identity that is generating the secret
+    - `{{random-N}}`: Random string of N characters
+
+    Allowed template functions are
+    - `truncate`: Truncates a string to a specified length
+    - `replace`: Replaces a substring with another value
+
+    Examples:
+    ```
+    {{randomUsername}}                              // 3POnzeFyK9gW2nioK0q2gMjr6CZqsRiX
+    {{unixTimestamp}}                               // 17490641580
+    {{identity.name}}                               // testuser
+    {{random-5}}                                    // x9k2m
+    {{truncate identity.name 4}}                    // test
+    {{replace identity.name 'user' 'replace'}}      // testreplace
+    ```
 	</ParamField>
 
 	![Dynamic Secret Setup Modal](../../../images/platform/dynamic-secrets/dynamic-secret-mongodb.png)