feat: conform the payload we send to form handler

Author: DNR500

app/services/subscriptions/pardot_form_handler_submitter.rb

@@ -17,7 +17,7 @@ def initialize(endpoint_url:)
     def call(form_payload:)
       return missing_configuration_result if endpoint_url.blank?
 
-      response = faraday.post(endpoint_url, form_payload)
+      response = faraday.post(endpoint_url, provider_payload(form_payload))
       Rails.logger.info(
         "[subscriptions#provider] status=#{response.status} " \
         "location=#{redirect_location(response)} " \
@@ -55,6 +55,14 @@ def missing_configuration_result
       )
     end
 
+    def provider_payload(form_payload)
+      # Map internal API contract to Pardot Form Handler external field names.
+      {
+        'email' => form_payload['email'],
+        'Tester' => form_payload['test_opt_in']
+      }.compact
+    end
+
     def classify_response(response)
       return reject_result unless SUCCESS_STATUS_CODES.include?(response.status)
       return Result.new(success?: true) if response.status == 200