updated readme with OAuth feature for public APIs

README.md

@@ -31,6 +31,26 @@ This library supports the following Java implementations:
 
 For Java 7 support, use `twilio-java` major version `7.X.X`.
 
+### Beta Annotation
+
+To indicate that a class or method is in beta and subject to change, we use the `@Beta` annotation. For example:
+
+```java
+
+@Beta
+public class ClassName {
+  // Class implementation
+}
+
+
+public class ClassName {
+  @Beta
+  public void init() {
+    // Implementation
+  }
+}
+```
+
 ## Installation
 
 `twilio-java` uses Maven. At present the jars _are_ available from a public [maven](https://mvnrepository.com/artifact/com.twilio.sdk/twilio) repository.
@@ -194,6 +214,25 @@ public class Example {
 }
 ```
 
+### OAuth Feature
+We are introducing Client Credentials Flow-based OAuth 2.0 authentication. 
+This feature is currently in beta and its implementation is subject to change.
+
+```java
+import com.twilio.credential.ClientCredentialProvider;
+
+public class Test {
+  public static void main(String[] args) {
+    String clientId = "YOUR_CLIENT_ID";
+    String clientSecret = "YOUR_CLIENT_SECRET";
+
+    Twilio.init(new ClientCredentialProvider(clientId, clientSecret));
+
+    // Make API requests here using the authenticated client
+  }
+}
+
+```
 ### Iterate through records
 
 The library automatically handles paging for you. With the `read` method, you can specify the number of records you want to receive (`limit`) and the maximum size you want each page fetch to be (`pageSize`). The library will then handle the task for you, fetching new pages under the hood as you iterate over the records.

src/main/java/com/twilio/Twilio.java

@@ -1,6 +1,6 @@
 package com.twilio;
 
-import com.twilio.annotations.Preview;
+import com.twilio.annotations.Beta;
 import com.twilio.auth_strategy.AuthStrategy;
 import com.twilio.constant.EnumConstants;
 import com.twilio.credential.ClientCredentialProvider;
@@ -73,16 +73,17 @@ public static synchronized void init(final String username, final String passwor
         Twilio.setAccountSid(null);
     }
 
+    @Beta
     public static synchronized void init(final CredentialProvider credentialProvider) {
         Twilio.setCredentialProvider(credentialProvider);
     }
 
+    @Beta
     public static synchronized void init(final CredentialProvider credentialProvider, String accountSid) {
         Twilio.setCredentialProvider(credentialProvider);
         Twilio.setAccountSid(accountSid);
     }
 
-    @Preview
     private static void setCredentialProvider(final CredentialProvider credentialProvider) {
         if (credentialProvider == null) {
             throw new AuthenticationException("Credential Provider can not be null");

src/main/java/com/twilio/TwilioNoAuth.java

@@ -1,13 +1,13 @@
 package com.twilio;
 
-import com.twilio.annotations.Preview;
+import com.twilio.annotations.Beta;
 import com.twilio.http.noauth.NoAuthTwilioRestClient;
 import lombok.Getter;
 
 import java.util.List;
 import com.twilio.exception.AuthenticationException;
 
-@Preview
+@Beta
 public class TwilioNoAuth {
     @Getter
     private static List<String> userAgentExtensions;

src/main/java/com/twilio/TwilioOrgsTokenAuth.java

@@ -1,6 +1,6 @@
 package com.twilio;
 
-import com.twilio.annotations.Preview;
+import com.twilio.annotations.Beta;
 import com.twilio.exception.AuthenticationException;
 import com.twilio.http.bearertoken.BearerTokenTwilioRestClient;
 import lombok.Getter;
@@ -12,7 +12,7 @@
 import com.twilio.http.bearertoken.TokenManager;
 import com.twilio.http.bearertoken.OrgsTokenManager;
 
-@Preview
+@Beta
 public class TwilioOrgsTokenAuth {
     private static String accessToken;
     @Getter

src/main/java/com/twilio/auth_strategy/TokenAuthStrategy.java

@@ -32,11 +32,10 @@ public void fetchToken() {
         if (this.token == null || this.token.isEmpty() || isTokenExpired(this.token)) {
             synchronized (TokenAuthStrategy.class){
                 if (this.token == null || this.token.isEmpty() || isTokenExpired(this.token)) {
-                    this.token = tokenManager.fetchAccessToken();
+                    this.token = tokenManager.fetchAccessToken(); // TODO: Exceptional handling
                 }
             }
         }
-        this.token = tokenManager.fetchAccessToken();
     }
 
     public boolean isTokenExpired(String token) {

src/main/java/com/twilio/credential/ClientCredentialProvider.java

@@ -1,6 +1,7 @@
 package com.twilio.credential;
 
 
+import com.twilio.annotations.Beta;
 import com.twilio.auth_strategy.AuthStrategy;
 import com.twilio.auth_strategy.TokenAuthStrategy;
 import com.twilio.constant.EnumConstants;
@@ -12,6 +13,7 @@
 import lombok.Getter;
 import lombok.Setter;
 
+@Beta
 public class ClientCredentialProvider extends CredentialProvider {
     private String grantType;
     private String clientId;

src/main/java/com/twilio/http/bearertoken/ApiTokenManager.java

@@ -1,9 +1,11 @@
 package com.twilio.http.bearertoken;
 
+import com.twilio.annotations.Beta;
 import com.twilio.exception.ApiException;
 import com.twilio.rest.previewiam.v1.Token;
 import com.twilio.rest.previewiam.v1.TokenCreator;
 
+@Beta
 public class ApiTokenManager implements TokenManager {
 
     private final String grantType;

src/main/java/com/twilio/http/bearertoken/OrgsTokenManager.java

@@ -1,10 +1,12 @@
 package com.twilio.http.bearertoken;
 
+import com.twilio.annotations.Beta;
 import lombok.Setter;
 import com.twilio.exception.ApiException;
 import lombok.RequiredArgsConstructor;
 import com.twilio.rest.previewiam.v1.Token;
 import com.twilio.rest.previewiam.v1.TokenCreator;
+@Beta
 public class OrgsTokenManager implements TokenManager{
 
     private final String grantType;