Add automatic parsing of emails with spreadsheets

We want to parse these email automatically so the Excel Analyzer runs
and detects issues with hidden data.

Fixes #8047

config/initializers/excel_analyzer.rb

@@ -1 +1,7 @@
 require "excel_analyzer"
+
+ExcelAnalyzer.on_spreadsheet_received = ->(raw_email_blob) do
+  incoming_message = IncomingMessage.joins(raw_email: :file_blob).
+    find_by(active_storage_blobs: { id: raw_email_blob })
+  incoming_message&.parse_raw_email!
+end

doc/CHANGES.md

@@ -2,6 +2,7 @@
 
 ## Highlighted Features
 
+* Add automatic parsing of emails contain Excel spreadsheets (Graeme Porteous)
 * Add admin list of all citations (Gareth Rees)
 * Improve redirection flow after user account closure actions (Gareth Rees)
 * Fix duplicated attachment masking jobs (Graeme Porteous)

spec/integration/incoming_mail_spec.rb

@@ -132,4 +132,26 @@
     expect(page.response_headers['Content-Type']).to eq("application/octet-stream; charset=utf-8")
     expect(page).to have_content "an unusual sort of file"
   end
+
+  it "does not automatically extract attachments after receiving email" do
+    receive_incoming_mail('incoming-request-plain.email',
+                          email_to: info_request.incoming_email)
+    perform_enqueued_jobs
+
+    im = info_request.incoming_messages.first
+    expect(im.foi_attachments).to be_empty
+  end
+
+  it "extract attachments when inbound email contains an Excel spreadsheet" do
+    mail = Mail.new(to: info_request.incoming_email) do
+      body 'My excel spreadsheet'
+      add_file 'gems/excel_analyzer/spec/fixtures/data.xlsx'
+    end
+
+    receive_incoming_mail(mail.to_s)
+    perform_enqueued_jobs
+
+    im = info_request.incoming_messages.first
+    expect(im.foi_attachments).to_not be_empty
+  end
 end