Update models to add support for new ContainerType for block actions

Author: Viktor Pelepiak

slack-base/src/main/java/com/hubspot/slack/client/models/interaction/Container.java

@@ -16,6 +16,7 @@
   {
     @Type(value = ViewContainer.class, name = "view"),
     @Type(value = MessageContainer.class, name = "message"),
+    @Type(value = MessageAttachmentContainer.class, name = "message_attachment"),
   }
 )
 public interface Container {

slack-base/src/main/java/com/hubspot/slack/client/models/interaction/ContainerType.java

@@ -7,6 +7,7 @@
 public enum ContainerType {
   VIEW,
   MESSAGE,
+  MESSAGE_ATTACHMENT,
   UNKNOWN;
 
   private static final EnumIndex<String, ContainerType> INDEX = new EnumIndex<>(

slack-base/src/main/java/com/hubspot/slack/client/models/interaction/MessageAttachmentContainerIF.java

@@ -0,0 +1,30 @@
+package com.hubspot.slack.client.models.interaction;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.hubspot.immutables.style.HubSpotStyle;
+import com.hubspot.slack.client.methods.params.chat.workobject.ExternalRef;
+import java.util.Optional;
+import org.immutables.value.Value;
+
+@Value.Immutable
+@HubSpotStyle
+@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
+public interface MessageAttachmentContainerIF extends Container {
+  String getMessageTs();
+
+  String getChannelId();
+
+  @JsonProperty("is_ephemeral")
+  boolean isEphemeral();
+
+  @JsonProperty("is_app_unfurl")
+  boolean isAppUnfurl();
+
+  int getAttachmentId();
+
+  Optional<ExternalRef> getExternalRef();
+
+  Optional<String> getEntityUrl();
+}