feat(block-kit): add card block example

block-kit/README.md

@@ -9,6 +9,7 @@ Read the [docs](https://docs.slack.dev/block-kit/) to learn concepts behind thes
 ### Blocks
 
 - **[Actions](https://docs.slack.dev/reference/block-kit/blocks/actions-block)**: Holds multiple interactive elements. [Implementation](./src/main/java/blocks/Actions.java).
+- **[Card](https://docs.slack.dev/reference/block-kit/blocks/card-block)**: Displays content in a card. [Implementation](./src/main/java/blocks/Card.java).
 - **[Context](https://docs.slack.dev/reference/block-kit/blocks/context-block)**: Provides contextual info, which can include both images and text. [Implementation](./src/main/java/blocks/Context.java).
 - **[Divider](https://docs.slack.dev/reference/block-kit/blocks/divider-block)**: Visually separates pieces of info inside of a message. [Implementation](./src/main/java/blocks/Divider.java).
 - **[File](https://docs.slack.dev/reference/block-kit/blocks/file-block)**: Displays info about remote files. [Implementation](./src/main/java/blocks/File.java).

block-kit/src/main/java/blocks/Card.java

@@ -0,0 +1,30 @@
+package blocks;
+
+import com.slack.api.model.block.Blocks;
+import com.slack.api.model.block.CardBlock;
+import com.slack.api.model.block.composition.BlockCompositions;
+import com.slack.api.model.block.element.BlockElements;
+import java.util.List;
+
+/**
+ * Displays content in a card.
+ * {@link https://docs.slack.dev/reference/block-kit/blocks/card-block/}
+ */
+public class Card {
+    /**
+     * A card with icon, title, subtitle, hero image, body, and an action button.
+     */
+    public static CardBlock example01() {
+        CardBlock block = Blocks.card(c -> c.icon(BlockElements.imageElement(
+                        i -> i.imageUrl("https://picsum.photos/36/36").altText("Icon")))
+                .title(BlockCompositions.markdownText("Lumon Industries"))
+                .subtitle(BlockCompositions.markdownText("Committed to work-life balance"))
+                .heroImage(BlockElements.imageElement(
+                        i -> i.imageUrl("https://picsum.photos/400/300").altText("Sample hero image")))
+                .body(BlockCompositions.markdownText("Please enjoy each card equally."))
+                .actions(List.of(BlockElements.button(b -> b.text(BlockCompositions.plainText(
+                                pt -> pt.text("Action Button").emoji(false)))
+                        .actionId("button_action")))));
+        return block;
+    }
+}

block-kit/src/test/java/blocks/CardTest.java

@@ -0,0 +1,55 @@
+package blocks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.google.gson.JsonParser;
+import com.slack.api.model.block.CardBlock;
+import com.slack.api.util.json.GsonFactory;
+import org.junit.jupiter.api.Test;
+
+public class CardTest {
+    @Test
+    public void testExample01() {
+        CardBlock block = Card.example01();
+        String actual = GsonFactory.createSnakeCase().toJson(block);
+        String expected = """
+            {
+              "type": "card",
+              "icon": {
+                "type": "image",
+                "image_url": "https://picsum.photos/36/36",
+                "alt_text": "Icon"
+              },
+              "title": {
+                "type": "mrkdwn",
+                "text": "Lumon Industries"
+              },
+              "subtitle": {
+                "type": "mrkdwn",
+                "text": "Committed to work-life balance"
+              },
+              "hero_image": {
+                "type": "image",
+                "image_url": "https://picsum.photos/400/300",
+                "alt_text": "Sample hero image"
+              },
+              "body": {
+                "type": "mrkdwn",
+                "text": "Please enjoy each card equally."
+              },
+              "actions": [
+                {
+                  "type": "button",
+                  "text": {
+                    "type": "plain_text",
+                    "text": "Action Button",
+                    "emoji": false
+                  },
+                  "action_id": "button_action"
+                }
+              ]
+            }
+            """;
+        assertEquals(JsonParser.parseString(expected), JsonParser.parseString(actual));
+    }
+}