Document the x-ms-enum-flags extension

extensions/index.md

@@ -8,6 +8,7 @@
 |[x-ms-client-name](https://github.com/Azure/autorest/blob/main/docs/extensions/readme.md#x-ms-client-name) | allows control over identifier names used in client-side code generation for parameters and schema properties. |AutoRest| |
 |[x-ms-code-generation-settings](https://github.com/Azure/autorest/blob/main/docs/extensions/readme.md#x-ms-code-generation-settings) | enables passing code generation settings via OpenAPI document |Autorest|  |
 |[x-ms-deprecation](x-ms-deprecation.md)| Provides additional information about a deprecated endpoint, schema, property, etc... | Kiota | |
+|[x-ms-enum-flags](x-ms-enum-flags.md)| Provides information about whether an enum is bitwise(flagged) and the expected serialization format | Kiota | |
 |[x-ms-external](https://github.com/Azure/autorest/blob/main/docs/extensions/readme.md#x-ms-external) | allows specific Definition Objects to be excluded from code generation |AutoRest| |
 |[x-ms-info-kiota](x-kiota-info.md)| Provides configuration information to the Kiota API client code generator| Kiota |
 |[x-ms-mutability](https://github.com/Azure/autorest/blob/main/docs/extensions/readme.md#x-ms-mutability) | provides insight to Autorest on how to generate code. It doesn't alter the modeling of what is actually sent on the wire. |AutoRest| |

extensions/x-ms-enum-flags.md

@@ -0,0 +1,56 @@
+# OpenAPI Extension: x-ms-enums-flags
+
+This extension enables API providers to specify an enum as a bitwise(flagged) enum as well as the format of serialization of the multiple selected values.
+
+## x-ms-enums-flags object
+
+### Properties
+
+Properties are optional unless specified otherwise.
+
+| name | type | description |
+|---|---|---|
+| isFlags | boolean | Whether or not the enum is bitwise(flagged). Default is `false`(same as not specifying the extension) |
+
+## Schema
+
+Below is a yaml representation of the JSON Schema that defines the shape of the `x-ms-deprecation` object.
+
+```yaml
+type: object
+properties:
+  isFlags:
+    type: boolean
+    default: false
+```
+
+## Example
+
+```yaml
+openapi: 3.0.3
+info:
+  title: OData Service for namespace microsoft.graph
+  description: This OData service is located at https://graph.microsoft.com/v1.0
+  version: 1.0.1
+paths:
+  '/foo'
+    operations:
+      get:
+servers:
+  - url: https://graph.microsoft.com/v1.0
+definitions:
+  Microsoft.Graph.Feature:
+    title: Feature
+    enum:
+      - Feature1
+      - Feature2
+      - Feature3
+      - Feature4
+    type: string
+    x-ms-enum-flags:
+      isFlags: true
+```
+
+Used by: (informational)
+
+* [Microsoft Kiota](https://aka.ms/kiota)