Add actionpack-xml_parser to Gemfile.saas (production bundle)

The prior commit added it to saas/Gemfile but the production Docker
build uses Gemfile.saas (via BUNDLE_GEMFILE). This ensures the XML
parameter parser is present in the actual runtime environment.

Gemfile.saas

@@ -4,6 +4,7 @@ eval_gemfile "Gemfile"
 git_source(:bc) { |repo| "https://github.com/basecamp/#{repo}" }
 
 gem "activeresource", require: "active_resource"
+gem "actionpack-xml_parser" # needed by queenbee for XML request body parsing
 gem "stripe", "~> 18.0"
 gem "queenbee", bc: "queenbee-plugin"
 gem "fizzy-saas", path: "saas"

Gemfile.saas.lock

@@ -188,6 +188,9 @@ GEM
   specs:
     action_text-trix (2.1.16)
       railties
+    actionpack-xml_parser (2.0.1)
+      actionpack (>= 5.0)
+      railties (>= 5.0)
     activemodel-serializers-xml (1.0.3)
       activemodel (>= 5.0.0.a)
       activesupport (>= 5.0.0.a)
@@ -643,6 +646,7 @@ PLATFORMS
   x86_64-linux-musl
 
 DEPENDENCIES
+  actionpack-xml_parser
   activeresource
   audits1984!
   autotuner