[App Config] FeatureFlag and SecretReference support (#14342)

Reference: Azure/azure-sdk-for-net#18487
This PR adds the 
- [x] FeatureFlag support
- [x] SecretReference support
- [x] Tests for both
- [x] Samples for both
- [x] Changelog 
- [x] Links to the samples in the readme

sdk/appconfiguration/app-configuration/CHANGELOG.md

@@ -1,9 +1,13 @@
 # Release History
 
-## 1.2.0-beta.1 (Unreleased)
+## 1.2.0-beta.1 (2021-04-06)
 
+### New Features
+
+- New `SecretReferenceConfigurationSetting` and `FeatureFlagConfigurationSetting`types to represent configuration settings that references KeyVault Secret reference and feature flag respectively.
+  [#14342](https://github.com/Azure/azure-sdk-for-js/pull/14342)
 - Added `updateSyncToken` method to `AppConfigurationClient` to be able to provide external synchronization tokens.
-  [PR #14507](https://github.com/Azure/azure-sdk-for-js/pull/14507)
+  [#14507](https://github.com/Azure/azure-sdk-for-js/pull/14507)
 
 ## 1.1.1 (2021-03-25)
 

sdk/appconfiguration/app-configuration/README.md

@@ -159,6 +159,8 @@ The following samples show you the various ways you can interact with App Config
 - [`setReadOnlySample.ts`](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/typescript/src/setReadOnlySample.ts) - Marking settings as read-only to prevent modification.
 - [`getSettingOnlyIfChanged.ts`](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/typescript/src/getSettingOnlyIfChanged.ts) - Get a setting only if it changed from the last time you got it.
 - [`listRevisions.ts`](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/typescript/src/listRevisions.ts) - List the revisions of a key, allowing you to see previous values and when they were set.
+- [`secretReference.ts`](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/typescript/src/secretReference.ts) - SecretReference represents a configuration setting that references as KeyVault secret.
+- [`featureFlag.ts`](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/typescript/src/featureFlag.ts) - Feature flags are settings that follow specific JSON schema for the value.
 
 More in-depth examples can be found in the [samples](https://github.com/Azure/azure-sdk-for-js/tree/master/sdk/appconfiguration/app-configuration/samples/v1/) folder on GitHub.
 

sdk/appconfiguration/app-configuration/package.json

@@ -2,7 +2,7 @@
   "name": "@azure/app-configuration",
   "author": "Microsoft Corporation",
   "description": "An isomorphic client library for the Azure App Configuration service.",
-  "version": "1.1.1",
+  "version": "1.2.0-beta.1",
   "sdk-type": "client",
   "keywords": [
     "node",
@@ -96,6 +96,7 @@
     "@azure/dev-tool": "^1.0.0",
     "@azure/eslint-plugin-azure-sdk": "^3.0.0",
     "@azure/identity": "^1.1.0",
+    "@azure/keyvault-secrets": "^4.2.0-beta.4",
     "@azure/test-utils-recorder": "^1.0.0",
     "@microsoft/api-extractor": "7.7.11",
     "@rollup/plugin-commonjs": "11.0.2",