Test on the fix by rspamd/rspamd@4dd9c48

1. String cases: local.d/milter_headers.conf:

   skip_local = false;
   use = ['add-headers'];
   routines {
     add-headers {
       headers = {
         array = ['string1', 'string2'],
         string = 'string',
       }
     }
   }
   

   Result:

   Return-Path: <[email protected]>
   X-Original-To: ikeda
   Delivered-To: [email protected]
   Received: by slate.localdomain (Postfix, from userid 1000)
           id 1B99243216; Fri, 26 Aug 2022 06:57:43 +0000 (UTC)
   Message-Id: <[email protected]>
   Date: Fri, 26 Aug 2022 04:01:11 +0000 (UTC)
   From: ikeda <[email protected]>
   array: string1
   array: string2
   string: string
   

2. Hash cases: local.d/milter_headers.conf:

   skip_local = false;
   use = ['add-headers'];
   routines {
     add-headers {
       headers = {
         string = 'string',
         hash-0 = {value = 'string', order = 0},
         hash-1 = {value = 'string', order = 1},
         hash-2 = {value = 'string', order = -1},
         hash-3 = {value = 'string', order = nil},
         hash-4 = {value = 'string'},
       }
     }
   }
   

   Result:

   Return-Path: <[email protected]>
   X-Original-To: ikeda
   Delivered-To: [email protected]
   Received: by slate.localdomain (Postfix, from userid 1000)
           id 2624743216; Fri, 26 Aug 2022 06:54:59 +0000 (UTC)
   Message-Id: <[email protected]>
   Date: Fri, 26 Aug 2022 04:01:11 +0000 (UTC)
   From: ikeda <[email protected]>
   hash-2: string
   string: string
   hash-0: string
   hash-4: string
   hash-1: string
   hash-3: nil
   hash-3: string
   

   • Broken.

3. Array+hash cases: local.d/milter_headers.conf:

   skip_local = false;
   use = ['add-headers'];
   routines {
     add-headers {
       headers = {
         array = [
           'string',
           {value = 'hash-0', order = 0},
           {value = 'hash-1', order = 1},
           {value = 'hash-2', order = -1},
           {value = 'hash-3', order = nil},
           {value = 'hash-4'},
         ]
       }
     }
   }
   

   Result:

   Return-Path: <[email protected]>
   X-Original-To: ikeda
   Delivered-To: [email protected]
   array: hash-3
   array: hash-0
   array: hash-1
   Received: by slate.localdomain (Postfix, from userid 1000)
           id 8560143216; Fri, 26 Aug 2022 06:47:25 +0000 (UTC)
   array: hash-2
   Message-Id: <[email protected]>
   Date: Fri, 26 Aug 2022 04:01:11 +0000 (UTC)
   From: ikeda <[email protected]>
   array: string
   array: hash-4
   

   • hash-2 with order = -1 looks inserted in wrong position.