ref(slack): Handle getsentry billing attachment in block kit (#61874)

If getsentry adds a billing attachment to Slack, add it to the blocks.

[Here](https://github.com/getsentry/getsentry/pull/12401) is the
companion getsentry PR, but this one needs to be merged first.

Closes #61457

src/sentry/integrations/slack/actions/notification.py

@@ -55,7 +55,6 @@ class SlackNotifyServiceAction(IntegrationEventAction):
 
         def send_notification(event: GroupEvent, futures: Sequence[RuleFuture]) -> None:
             rules = [f.rule for f in futures]
-            # TODO: handle additional_attachments for block kit
             if features.has("organizations:slack-block-kit", event.group.project.organization):
                 blocks = build_group_attachment(
                     event.group,
@@ -64,6 +63,12 @@ class SlackNotifyServiceAction(IntegrationEventAction):
                     rules=rules,
                     notification_uuid=notification_uuid,
                 )
+                additional_attachment = get_additional_attachment(
+                    integration, self.project.organization
+                )
+                if additional_attachment:
+                    for block in additional_attachment:
+                        blocks["blocks"].append(block)
 
                 if blocks.get("blocks"):
                     payload = {

src/sentry/integrations/slack/message_builder/base/block.py

@@ -76,6 +76,23 @@ class BlockSlackMessageBuilder(SlackMessageBuilder, ABC):
 
         return button
 
+    @staticmethod
+    def get_link_button(action):
+        return {
+            "type": "section",
+            "text": {
+                "type": "mrkdwn",
+                "text": action.label,
+            },
+            "accessory": {
+                "type": "button",
+                "text": {"type": "plain_text", "text": action.name, "emoji": True},
+                "style": action.style,
+                "value": action.value,
+                "url": action.url,
+            },
+        }
+
     @staticmethod
     def get_action_block(actions: Sequence[Tuple[str, Optional[str], str]]) -> SlackBlock:
         class SlackBlockType(TypedDict):

src/sentry/integrations/slack/webhooks/action.py

@@ -500,8 +500,8 @@ class SlackActionEndpoint(Endpoint):
 
         action_option = self.get_action_option(slack_request=slack_request)
 
-        # If a user is just clicking our auto response in the messages tab we just return a 200
-        if action_option == "sentry_docs_link_clicked":
+        # If a user is just clicking a button link we return a 200
+        if action_option in ("sentry_docs_link_clicked", "grace_period_warning"):
             return self.respond()
 
         if action_option in UNFURL_ACTION_OPTIONS: