Chore: Routine Bugfixes and enhancements (#979)

- Fix slack scopes
- Docs for authentication
Fixes: #704 , #973

lib/integrations/slack/channel_builder.rb

@@ -17,10 +17,7 @@ class Integrations::Slack::ChannelBuilder
   end
 
   def slack_client
-    Slack.configure do |config|
-      config.token = hook.access_token
-    end
-    Slack::Web::Client.new
+    @slack_client ||= Slack::Web::Client.new(token: hook.access_token)
   end
 
   def find_or_create_channel
@@ -29,6 +26,7 @@ class Integrations::Slack::ChannelBuilder
   end
 
   def update_reference_id
-    @hook.update(reference_id: channel['id'])
+    slack_client.conversations_join(channel: channel[:id])
+    @hook.update(reference_id: channel[:id])
   end
 end