more extensible oauth filter

src/main/java/com/inteligr8/rs/OAuthAuthorizationFilter.java

@@ -101,6 +101,7 @@ public abstract class OAuthAuthorizationFilter implements AuthorizationFilter {
 			form.param("client_secret", this.clientSecret);
 		if (this.scope != null)
 			form.param("scope", this.scope);
+		this.extendRefreshTokenForm(form);
 		
 		Entity<Form> entity = Entity.form(form);
 		
@@ -118,6 +119,7 @@ public abstract class OAuthAuthorizationFilter implements AuthorizationFilter {
 		this.accessToken = (String)response.get("access_token");
 		this.expiration = System.currentTimeMillis() + ((Number)response.get("expires_in")).longValue() * 1000L;
 		this.refreshToken = (String)response.get("refresh_token");
+		this.extendRefreshTokenResponse(response);
 	}
 	
 	protected Form createRefreshForm() {
@@ -126,5 +128,11 @@ public abstract class OAuthAuthorizationFilter implements AuthorizationFilter {
 	}
 	
 	protected abstract Form createForm();
+	
+	protected void extendRefreshTokenForm(Form form) {
+	}
+	
+	protected void extendRefreshTokenResponse(Map<String, Object> response) {
+	}
 
 }