feat: privacy mode

Adds support for hiding IP addresses & hostnames associated with clients sending
authenticated mail in to Postal over SMTP and HTTP

spec/lib/postal/received_header_spec.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+describe Postal::ReceivedHeader do
+  before do
+    allow(Resolv::DNS).to receive(:open).and_return("hostname.com")
+  end
+
+  describe ".generate" do
+    context "when server is nil" do
+      it "returns the correct string" do
+        result = described_class.generate(nil, "testhelo", "1.1.1.1", :smtp)
+        expect(result).to eq "from testhelo (hostname.com [1.1.1.1]) " \
+                             "by #{Postal.config.dns.smtp_server_hostname} " \
+                             "with SMTP; #{Time.now.utc.rfc2822}"
+      end
+    end
+
+    context "when server is provided with privacy_mode=true" do
+      it "returns the correct string" do
+        server = Server.new(privacy_mode: true)
+        result = described_class.generate(server, "testhelo", "1.1.1.1", :smtp)
+        expect(result).to eq "by #{Postal.config.dns.smtp_server_hostname} " \
+                             "with SMTP; #{Time.now.utc.rfc2822}"
+      end
+    end
+
+    context "when server is provided with privacy_mode=false" do
+      it "returns the correct string" do
+        server = Server.new(privacy_mode: false)
+        result = described_class.generate(server, "testhelo", "1.1.1.1", :smtp)
+        expect(result).to eq "from testhelo (hostname.com [1.1.1.1]) " \
+                             "by #{Postal.config.dns.smtp_server_hostname} " \
+                             "with SMTP; #{Time.now.utc.rfc2822}"
+      end
+    end
+
+    context "when type is http" do
+      it "returns the correct string" do
+        result = described_class.generate(nil, "web-ui", "1.1.1.1", :http)
+        expect(result).to eq "from web-ui (hostname.com [1.1.1.1]) " \
+                             "by #{Postal.config.web.host} " \
+                             "with HTTP; #{Time.now.utc.rfc2822}"
+      end
+    end
+  end
+end