fix: don't use Maglev to process websocket related requests

Author: did

lib/maglev/preview_constraint.rb

@@ -13,7 +13,7 @@ def initialize(preview_host: nil)
     end
 
     def matches?(request)
-      (accepted_format?(request) || crawler?(request)) && match_host?(request)
+      !websocket?(request) && (accepted_format?(request) || crawler?(request)) && match_host?(request)
     end
 
     protected
@@ -32,6 +32,10 @@ def crawler?(request)
       request.format.symbol.nil? && CRAWLER_USER_AGENTS.match?(request.user_agent)
     end
 
+    def websocket?(request)
+      request.headers['Upgrade'] == 'websocket'
+    end
+
     def match_host?(request)
       !preview_host || preview_host == request.host
     end