feat: new configuration system (and schema) (#2819)

app/models/concerns/has_dns_checks.rb

@@ -49,10 +49,10 @@ module HasDNSChecks
       self.spf_status = "Missing"
       self.spf_error = "No SPF record exists for this domain"
     else
-      suitable_spf_records = spf_records.grep(/include:\s*#{Regexp.escape(Postal.config.dns.spf_include)}/)
+      suitable_spf_records = spf_records.grep(/include:\s*#{Regexp.escape(Postal::Config.dns.spf_include)}/)
       if suitable_spf_records.empty?
         self.spf_status = "Invalid"
-        self.spf_error = "An SPF record exists but it doesn't include #{Postal.config.dns.spf_include}"
+        self.spf_error = "An SPF record exists but it doesn't include #{Postal::Config.dns.spf_include}"
         false
       else
         self.spf_status = "OK"
@@ -108,11 +108,11 @@ module HasDNSChecks
       self.mx_status = "Missing"
       self.mx_error = "There are no MX records for #{name}"
     else
-      missing_records = Postal.config.dns.mx_records.dup - records.map { |r| r.to_s.downcase }
+      missing_records = Postal::Config.dns.mx_records.dup - records.map { |r| r.to_s.downcase }
       if missing_records.empty?
         self.mx_status = "OK"
         self.mx_error = nil
-      elsif missing_records.size == Postal.config.dns.mx_records.size
+      elsif missing_records.size == Postal::Config.dns.mx_records.size
         self.mx_status = "Missing"
         self.mx_error = "You have MX records but none of them point to us."
       else
@@ -136,12 +136,12 @@ module HasDNSChecks
     if records.empty?
       self.return_path_status = "Missing"
       self.return_path_error = "There is no return path record at #{return_path_domain}"
-    elsif records.size == 1 && records.first == Postal.config.dns.return_path
+    elsif records.size == 1 && records.first == Postal::Config.dns.return_path_domain
       self.return_path_status = "OK"
       self.return_path_error = nil
     else
       self.return_path_status = "Invalid"
-      self.return_path_error = "There is a CNAME record at #{return_path_domain} but it points to #{records.first} which is incorrect. It should point to #{Postal.config.dns.return_path}."
+      self.return_path_error = "There is a CNAME record at #{return_path_domain} but it points to #{records.first} which is incorrect. It should point to #{Postal::Config.dns.return_path_domain}."
     end
   end