Add link to Fizzy to Slack message

This makes it nice to use with a Slack webhook enabled, see
also this discussion: https://github.com/basecamp/fizzy/discussions/2238

app/models/event/description.rb

@@ -14,7 +14,7 @@ class Event::Description
   end
 
   def to_plain_text
-    to_sentence(creator_name, h(card.title))
+    to_sentence(creator_name, quoted(card.title))
   end
 
   private
@@ -41,6 +41,10 @@ class Event::Description
       h(event.creator.name)
     end
 
+    def quoted(text)
+      %("#{h text}")
+    end
+
     def card
       @card ||= event.action.comment_created? ? event.eventable.card : event.eventable
     end

app/models/webhook/delivery.rb

@@ -1,4 +1,6 @@
 class Webhook::Delivery < ApplicationRecord
+  include Rails.application.routes.url_helpers
+
   class ResponseTooLarge < StandardError; end
 
   STALE_TRESHOLD = 7.days
@@ -130,8 +132,7 @@ class Webhook::Delivery < ApplicationRecord
       elsif webhook.for_campfire?
         render_payload(formats: :html)
       elsif webhook.for_slack?
-        html = render_payload(formats: :html)
-        { text: convert_html_to_mrkdwn(html) }.to_json
+        slack_payload
       else
         render_payload(formats: :json)
       end
@@ -158,4 +159,16 @@ class Webhook::Delivery < ApplicationRecord
 
       document.text
     end
+
+    def slack_payload
+      text = event.description_for(nil).to_plain_text
+      url = polymorphic_url(event.eventable, base_url_options.merge(script_name: account.slug))
+
+      { text: "#{text} <#{url}|Open in Fizzy>" }.to_json
+    end
+
+    def base_url_options
+      Rails.application.routes.default_url_options.presence ||
+        Rails.application.config.action_mailer.default_url_options
+    end
 end