fix: register the type adapter to parse messages as expected

Author: zimeg

slack-api-client/src/main/java/com/slack/api/util/json/GsonFactory.java

@@ -9,6 +9,7 @@
 import com.slack.api.model.File;
 import com.slack.api.model.admin.AppWorkflow;
 import com.slack.api.model.block.ContextBlockElement;
+import com.slack.api.model.block.ContextActionsBlockElement;
 import com.slack.api.model.block.LayoutBlock;
 import com.slack.api.model.block.composition.TextObject;
 import com.slack.api.model.block.element.BlockElement;
@@ -75,6 +76,7 @@ public static void registerTypeAdapters(GsonBuilder builder, boolean failOnUnkno
                 .registerTypeAdapter(LayoutBlock.class, new GsonLayoutBlockFactory(failOnUnknownProps))
                 .registerTypeAdapter(TextObject.class, new GsonTextObjectFactory(failOnUnknownProps))
                 .registerTypeAdapter(ContextBlockElement.class, new GsonContextBlockElementFactory(failOnUnknownProps))
+                .registerTypeAdapter(ContextActionsBlockElement.class, new GsonContextActionsBlockElementFactory(failOnUnknownProps))
                 .registerTypeAdapter(BlockElement.class, new GsonBlockElementFactory(failOnUnknownProps))
                 .registerTypeAdapter(RichTextElement.class, new GsonRichTextElementFactory(failOnUnknownProps))
                 .registerTypeAdapter(FunctionExecutedEvent.InputValue.class, new GsonFunctionExecutedEventInputValueFactory())