add connect api to how to and remove not supporting room

Author: huachuandeng

articles/communication-services/concepts/call-automation/call-automation.md

@@ -13,9 +13,6 @@ ms.author: askaur
 
 Azure Communication Services Call Automation provides developers the ability to build server-based, intelligent call workflows, and call recording for voice and Public Switched Telephone Network(PSTN) channels. The SDKs, available in C#, Java, JavaScript and Python, use an action-event model to help you build personalized customer interactions. Your communication applications can listen to real-time call events and perform control plane actions (like answer, transfer, play audio, start recording, etc.) to steer and control calls based on your business logic.
 
-> [!NOTE]
-> Call Automation currently doesn't support [Rooms](../rooms/room-concept.md) calls.
-
 ## Common use cases
 
 Some of the common use cases that can be built using Call Automation include:

articles/communication-services/how-tos/call-automation/actions-for-call-control.md

@@ -18,9 +18,6 @@ Call Automation uses a REST API interface to receive requests for actions and pr
 
 Call Automation supports various other actions to manage call media and recording that have separate guides.
 
-> [!NOTE]
-> Call Automation currently doesn't support [Rooms](../../concepts/rooms/room-concept.md) calls.
-
 As a prerequisite, we recommend you to read these articles to make the most of this guide:
 
 1. Call Automation [concepts guide](../../concepts/call-automation/call-automation.md#call-actions) that describes the action-event programming model and event callbacks.
@@ -169,6 +166,125 @@ The response provides you with CallConnection object that you can use to take fu
 2. `ParticipantsUpdated` event that contains the latest list of participants in the call.
 ![Sequence diagram for placing an outbound call.](media/make-call-flow.png)
 
+## Connect to a call
+
+You can connect to a call using a call locator. When connecting a call, it's necessary to provide a callback url. Communication Services post all subsequent events about this call to that url.
+
+Currently, we have 3 different CallLocators：
+
+Connecting to a call using ServerCallLocator
+### [csharp](#tab/csharp)
+
+```csharp
+Uri callbackUri = new Uri("https://<myendpoint>/Events"); //the callback endpoint where you want to receive subsequent events
+CallLocator serverCallLocator = new ServerCallLocator("<ServerCallId>");
+ConnctCallResult response = await client.ConnectAsync(serverCallLocator, callbackUri);
+```
+
+### [Java](#tab/java)
+
+```java
+String callbackUri = "https://<myendpoint>/Events"; //the callback endpoint where you want to receive subsequent events
+CallLocator serverCallLocator =  new ServerCallLocator("<ServerCallId>");
+ConnectCallResult response = client.connectCall(serverCallLocator, callbackUri).block();
+```
+
+### [JavaScript](#tab/javascript)
+
+```javascript
+const callbackUri = "https://<myendpoint>/Events"; // the callback endpoint where you want to receive subsequent events 
+const serverCallLocator = { kind: "serverCallLocator", id: "<serverCallId>" };
+const response = await client.connectCall(serverCallLocator, callbackUri);
+```
+
+### [Python](#tab/python)
+
+```python
+callback_uri = "https://<myendpoint>/Events"  # the callback endpoint where you want to receive subsequent events
+server_call_locator = ServerCallLocator("<server_call_id>")
+call_connection_properties = client.connect_call(call_locator=server_call_locator, callback_url=callback_uri)
+```
+
+-----
+
+Connecting to a call using GroupCallLocator
+### [csharp](#tab/csharp)
+
+```csharp
+Uri callbackUri = new Uri("https://<myendpoint>/Events"); //the callback endpoint where you want to receive subsequent events
+CallLocator groupCallLocator = new GroupCallLocator("<GroupCallId>");
+ConnctCallResult response = await client.ConnectAsync(groupCallLocator, callbackUri);
+```
+
+### [Java](#tab/java)
+
+```java
+String callbackUri = "https://<myendpoint>/Events"; //the callback endpoint where you want to receive subsequent events
+CallLocator groupCallLocator =  new GroupCallLocator("<GroupCallId>");
+ConnectCallResult response = client.connectCall(groupCallLocator, callbackUri).block();
+```
+
+### [JavaScript](#tab/javascript)
+
+```javascript
+const callbackUri = "https://<myendpoint>/Events"; // the callback endpoint where you want to receive subsequent events 
+const groupCallLocator = { kind: "groupCallLocator", id: "<groupCallId>" };
+const response = await client.connectCall(groupCallLocator, callbackUri);
+```
+
+### [Python](#tab/python)
+
+```python
+callback_uri = "https://<myendpoint>/Events"  # the callback endpoint where you want to receive subsequent events
+group_call_locator = GroupCallLocator("<group_call_id>")
+call_connection_properties = client.connect_call(call_locator=group_call_locator, callback_url=callback_uri)
+```
+
+-----
+
+Connecting to a call using RoomCallLocator
+### [csharp](#tab/csharp)
+
+```csharp
+Uri callbackUri = new Uri("https://<myendpoint>/Events"); //the callback endpoint where you want to receive subsequent events
+CallLocator roomCallLocator = new GroupCallLocator("<RoomId>");
+ConnctCallResult response = await client.ConnectAsync(roomCallLocator, callbackUri);
+```
+
+### [Java](#tab/java)
+
+```java
+String callbackUri = "https://<myendpoint>/Events"; //the callback endpoint where you want to receive subsequent events
+CallLocator roomCallLocator =  new RoomCallLocator("<RoomId>");
+ConnectCallResult response = client.connectCall(roomCallLocator, callbackUri).block();
+```
+
+### [JavaScript](#tab/javascript)
+
+```javascript
+const roomCallLocator = { kind: "roomCallLocator", id: "<RoomId>" };
+const callbackUri = "https://<myendpoint>/Events"; // the callback endpoint where you want to receive subsequent events 
+const response = await client.connectCall(roomCallLocator, callbackUri);
+```
+
+### [Python](#tab/python)
+
+```python
+callback_uri = "https://<myendpoint>/Events"  # the callback endpoint where you want to receive subsequent events
+room_call_locator = RoomCallLocator("<room_id>")
+call_connection_properties = client.connect_call(call_locator=room_call_locator, callback_url=callback_uri)
+```
+
+-----
+
+The response provides you with CallConnection object that you can use to take further actions on this call once it's connected. Once it connects to the call, two events are published to the callback endpoint you provided earlier:
+
+1. `CallConnected` event notifying that you have connected to the call.
+2. `ParticipantsUpdated` event that contains the latest list of participants in the call.
+
+![Sequence diagram for connecting to call.](media/connect-call-flow.png)
+
+
 ## Answer an incoming call
 
 Once you've subscribed to receive [incoming call notifications](../../concepts/call-automation/incoming-call-notification.md) to your resource, you will answer an incoming call. When answering a call, it's necessary to provide a callback url. Communication Services post all subsequent events about this call to that url.