Add the documentation stuff properly

Author: EraYaN

docs/generators/aspnet-fastendpoints.md

@@ -42,7 +42,8 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 
 | Extension name | Description | Applicable for | Default value |
 | -------------- | ----------- | -------------- | ------------- |
-|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used. Zero-based.|MODEL|false
+|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used, zero-based|MODEL|false
+
 
 ## IMPORT MAPPING
 

docs/generators/aspnetcore.md

@@ -60,7 +60,8 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 
 | Extension name | Description | Applicable for | Default value |
 | -------------- | ----------- | -------------- | ------------- |
-|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used. Zero-based.|MODEL|false
+|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used, zero-based|MODEL|false
+
 
 ## IMPORT MAPPING
 

docs/generators/csharp-functions.md

@@ -52,7 +52,8 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 
 | Extension name | Description | Applicable for | Default value |
 | -------------- | ----------- | -------------- | ------------- |
-|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used. Zero-based.|MODEL|false
+|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used, zero-based|MODEL|false
+
 
 ## IMPORT MAPPING
 

docs/generators/csharp.md

@@ -61,7 +61,8 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 
 | Extension name | Description | Applicable for | Default value |
 | -------------- | ----------- | -------------- | ------------- |
-|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used. Zero-based.|MODEL|false
+|x-zero-based-enum|When used on an enum, the index will not be generated and the default numbering will be used, zero-based|MODEL|false
+
 
 ## IMPORT MAPPING
 

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

@@ -24,6 +24,7 @@ public enum VendorExtension {
     X_OPERATION_EXTRA_ANNOTATION("x-operation-extra-annotation", ExtensionLevel.OPERATION, "List of custom annotations to be added to operation", null),
     X_VERSION_PARAM("x-version-param", ExtensionLevel.OPERATION_PARAMETER, "Marker property that tells that this parameter would be used for endpoint versioning. Applicable for headers & query params. true/false", null),
     X_PATTERN_MESSAGE("x-pattern-message", Arrays.asList(ExtensionLevel.FIELD, ExtensionLevel.OPERATION_PARAMETER), "Add this property whenever you need to customize the invalidation error message for the regex pattern of a variable", null),
+    X_ZERO_BASED_ENUM("x-zero-based-enum", ExtensionLevel.MODEL, "When used on an enum, the index will not be generated and the default numbering will be used, zero-based", "false"),
     ;
 
     private final String name;

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

@@ -105,7 +105,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen {
     protected boolean supportNullable = Boolean.FALSE;
 
     @Setter protected Boolean zeroBasedEnums = null;
-    protected static final String zeroBasedEnumVendorExtension = "x-zero-based-enum";
+    protected static final String zeroBasedEnumVendorExtension = VendorExtension.X_ZERO_BASED_ENUM.getName();
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractCSharpCodegen.class);
 
@@ -2033,6 +2033,13 @@ protected Set<String> getNullableTypes() {
         throw new RuntimeException("This method should no longer be used.");
     }
 
+    @Override
+    public List<VendorExtension> getSupportedVendorExtensions() {
+        List<VendorExtension> extensions = super.getSupportedVendorExtensions();
+        extensions.add(VendorExtension.X_ZERO_BASED_ENUM);
+        return extensions;
+    }
+
     protected Set<String> getValueTypes() {
         return new HashSet<>(Arrays.asList("decimal", "bool", "int", "uint", "long", "ulong", "float", "double", "DateTime", "DateOnly", "DateTimeOffset", "Guid"));
     }