[Postfix] Add mailcow_anonymize_headers to default config

data/conf/postfix/mailcow_anonymize_headers.pcre

@@ -0,0 +1,7 @@
+/^\s*Received:.*Authenticated sender:(.+)/
+    REPLACE Received: from localhost (localhost [127.0.0.1]) (Authenticated sender:$1
+/^\s*User-Agent/        IGNORE
+/^\s*X-Enigmail/        IGNORE
+/^\s*X-Mailer/          IGNORE
+/^\s*X-Originating-IP/  IGNORE
+/^\s*X-Forward/         IGNORE

data/conf/postfix/main.cf

@@ -129,3 +129,4 @@ smtp_sasl_password_maps = proxy:mysql:/opt/postfix/conf/sql/mysql_sasl_passwd_ma
 smtp_sasl_security_options = 
 smtp_sasl_mechanism_filter = plain, login
 smtp_tls_policy_maps=proxy:mysql:/opt/postfix/conf/sql/mysql_tls_policy_override_maps.cf
+smtp_header_checks = pcre:/opt/postfix/conf/mailcow_anonymize_headers.pcre