Modify rule S6656: Add missing message and highlighting info (#2668)

## Review

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- [ ] logical errors and incorrect information
- [ ] information gaps and missing content
- [ ] text style and tone
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guidelines](https://github.com/SonarSource/rspec/#to-modify-an-existing-rule)

rules/S6656/azureresourcemanager/rule.adoc

@@ -18,4 +18,28 @@ include::how-to-fix-it/arm.adoc[]
 
 === Standards
 * https://cwe.mitre.org/data/definitions/200[MITRE, CWE-200] - Exposure of Sensitive Information to an Unauthorized Actor
-* https://cwe.mitre.org/data/definitions/532[MITRE, CWE-532] - Insertion of Sensitive Information into Log File
+* https://cwe.mitre.org/data/definitions/532[MITRE, CWE-532] - Insertion of Sensitive Information into Log File
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+=== Message
+==== Primary Message
+Change this code to not use an outer expression evaluation scope in nested templates.
+
+==== Secondary Message
+This secure parameter is leaked through the deployment history.
+
+=== Highlighting
+==== Primary Highlight
+If `properties.expressionEvaluationOptions.scope` is set to an incorrect value, then highlight the `properties.expressionEvaluationOptions.scope` property.
+
+If `properties.expressionEvaluationOptions.scope` or `properties.expressionEvaluationOptions` is not set at all, then highlight `properties` entirely (of the `"Microsoft.Resources/deployments"` resource where it should be set.)
+
+==== Secondary Highlight
+Highlight the secure parameter in the nested template that is at risk here.
+
+endif::env-github,rspecator-view[]