better wordings for CLASS_MODIFIER (#7233)

Author: wing328

docs/generators/aspnetcore.md

@@ -7,7 +7,7 @@ sidebar_label: aspnetcore
 | ------ | ----------- | ------ | ------- |
 |aspnetCoreVersion|ASP.NET Core version: 3.1, 3.0, 2.2, 2.1, 2.0 (deprecated)| |2.2|
 |buildTarget|Target to build an application or library| |program|
-|classModifier|Class Modifier can be empty, abstract| ||
+|classModifier|Class Modifier for controller classes: Empty string or abstract.| ||
 |compatibilityVersion|ASP.Net Core CompatibilityVersion| |Version_2_2|
 |enumNameSuffix|Suffix that will be appended to all enum names.| |Enum|
 |enumValueSuffix|Suffix that will be appended to all enum values.| |Enum|

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AspNetCoreServerCodegen.java

@@ -69,7 +69,7 @@ public class AspNetCoreServerCodegen extends AbstractCSharpCodegen {
     protected String serverHost = "0.0.0.0";
     protected CliOption swashbuckleVersion = new CliOption(SWASHBUCKLE_VERSION, "Swashbuckle version: 3.0.0, 4.0.0, 5.0.0");
     protected CliOption aspnetCoreVersion = new CliOption(ASPNET_CORE_VERSION, "ASP.NET Core version: 3.1, 3.0, 2.2, 2.1, 2.0 (deprecated)");
-    private CliOption classModifier = new CliOption(CLASS_MODIFIER, "Class Modifier can be empty, abstract");
+    private CliOption classModifier = new CliOption(CLASS_MODIFIER, "Class Modifier for controller classes: Empty string or abstract.");
     private CliOption operationModifier = new CliOption(OPERATION_MODIFIER, "Operation Modifier can be virtual or abstract");
     private CliOption modelClassModifier = new CliOption(MODEL_CLASS_MODIFIER, "Model Class Modifier can be nothing or partial");
     private boolean generateBody = true;