[Cosmos] Add preferred regions to CosmosClientOptions (#22206)

* added to client options, added sample

* pointers lol

* Update example_test.go

sdk/data/azcosmos/cosmos_client_options.go

@@ -13,4 +13,6 @@ type ClientOptions struct {
 	// When EnableContentResponseOnWrite is false will cause the response to have a null resource. This reduces networking and CPU load by not sending the resource back over the network and serializing it on the client.
 	// The default is false.
 	EnableContentResponseOnWrite bool
+	// PreferredRegions is a list of regions to be used when initializing the client in case the default region fails.
+	PreferredRegions []string
 }

sdk/data/azcosmos/example_test.go

@@ -78,6 +78,33 @@ func ExampleNewClientFromConnectionString() {
 	fmt.Println(client)
 }
 
+func ExampleClientOptions_PreferredRegions() {
+	clientOptions := azcosmos.ClientOptions{PreferredRegions: []string{"West US", "Central US"}}
+
+	endpoint, ok := os.LookupEnv("AZURE_COSMOS_ENDPOINT")
+	if !ok {
+		panic("AZURE_COSMOS_ENDPOINT could not be found")
+	}
+
+	key, ok := os.LookupEnv("AZURE_COSMOS_KEY")
+	if !ok {
+		panic("AZURE_COSMOS_KEY could not be found")
+	}
+
+	// Create new Cosmos DB client.
+	cred, err := azcosmos.NewKeyCredential(key)
+	if err != nil {
+		panic(err)
+	}
+
+	client, err := azcosmos.NewClientWithKey(endpoint, cred, &clientOptions)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(client)
+}
+
 func ExampleClient_CreateDatabase() {
 	endpoint, ok := os.LookupEnv("AZURE_COSMOS_ENDPOINT")
 	if !ok {