feat: add is_hidden property to calc groups and calculated members

Author: stanislavtrifonov88

sml-reference/dimension.md

@@ -281,11 +281,13 @@ namespace Dimensions{
       String description
       String folder
       Array~CalculatedMembers~ calculated_members
+      Boolean is_hidden
     }
     class CalculatedMembers{
       String unique_name
       String description
       String format
+      Boolean is_hidden
       String expression
       Boolean use_input_metric_format
     }
@@ -513,6 +515,18 @@ Defines the individual calculated members in the group.
 
 A description of the calculation group.
 
+## is_hidden
+
+- **Type:** boolean
+- **Required:** N
+
+Determines whether the attribute is visible in BI tools. 
+
+Supported values:
+
+- `false` (default)
+- `true`
+
 # Calculated Members Properties
 
 ## unique_name
@@ -542,6 +556,18 @@ Supported templates:
 
 If you do not want to use a built-in template, you can define a custom expression using the `expression` property (see below).
 
+## is_hidden
+
+- **Type:** boolean
+- **Required:** N
+
+Determines whether the attribute is visible in BI tools. 
+
+Supported values:
+
+- `false` (default)
+- `true`
+
 ## expression
 
 - **Type:** string