Add convenience method for reuseRefreshToken()

Longer term (2.1.0) we should pull out the toke service builing into
a separate builder. It's too big a change for a point release though.

Fixes gh-318

spring-security-oauth2/src/main/java/org/springframework/security/oauth2/config/annotation/web/configurers/AuthorizationServerEndpointsConfigurer.java

@@ -107,6 +107,8 @@ public final class AuthorizationServerEndpointsConfigurer {
 
 	private boolean tokenServicesOverride = false;
 
+	private boolean reuseRefreshToken;
+
 	public AuthorizationServerTokenServices getTokenServices() {
 		return tokenServices;
 	}
@@ -153,6 +155,11 @@ public AuthorizationServerEndpointsConfigurer tokenEnhancer(TokenEnhancer tokenE
 		return this;
 	}
 
+	public AuthorizationServerEndpointsConfigurer reuseRefreshTokens() {
+		this.reuseRefreshToken = true;
+		return this;
+	}
+
 	public AuthorizationServerEndpointsConfigurer accessTokenConverter(AccessTokenConverter accessTokenConverter) {
 		this.accessTokenConverter = accessTokenConverter;
 		return this;
@@ -307,6 +314,7 @@ private DefaultTokenServices createDefaultTokenServices() {
 		DefaultTokenServices tokenServices = new DefaultTokenServices();
 		tokenServices.setTokenStore(tokenStore());
 		tokenServices.setSupportRefreshToken(true);
+		tokenServices.setReuseRefreshToken(reuseRefreshToken);
 		tokenServices.setClientDetailsService(clientDetailsService());
 		tokenServices.setTokenEnhancer(tokenEnhancer());
 		return tokenServices;