Further improvements on extra services configured in master.cf

As promised in PR #75, here's a further (and hopefully final)
iteration of the master.cf service handling:

- Bring dovecot and policyd-spf configuration in line with the
  extras_services item added in PR #75
- Remove policyd-spf configuration again from services.jinja,
  handle this in master.cf instead, where it was before
- Allow for completely custom services to be added via a pillar
  definition in postfix:master_config:services
- Fix legacy dovecot argv example in pillar.example: The example
  showed the extra_args being defined as part of the argv
  parameter, something that would clash with the actual code and
  result in a duplicate '-d ${recipient}' definition in the config.

pillar.example

@@ -7,7 +7,7 @@ postfix:
       user: vmail
       group: vmail
       flags: DRhu
-      argv: "/usr/lib/dovecot/deliver -d ${recipient}"
+      argv: "/usr/lib/dovecot/deliver"
 
     enable_submission: False
     # To replace the defaults use this:
@@ -36,6 +36,14 @@ postfix:
         chroot: True
       uucp:
 	enable: True
+      custom-mda:
+        argv: /usr/local/sbin/mail-handler.py
+        command: pipe
+        extras: --rcpt ${recipient}
+        flags: DRhu
+        user: mail
+        # Wrap the output in master.cf at 78 chars for better readability
+        wrap: True
 
   enable_service: True
   reload_service: True

postfix/files/master.cf

@@ -111,13 +111,12 @@ y
 {%-   endif %}
 {%- endfor %}
 #
-{%- macro extra_service(service_name, wrap=False, force_enable=False) -%}
+{%- set handled_extra_services = [] -%}
+{%- macro extra_service(service_name, wrap=False) -%}
+{%-   do handled_extra_services.append(service_name) -%}
 {%-   set service = salt['pillar.get']('postfix:master_config:services:%s' % (
                                          service_name,),
                                          postfix_master_services_defaults[service_name]) -%}
-{%-   if force_enable -%}
-{%-     do service.update({'enable': True}) -%}
-{%-   endif -%}
 {%-   if service.get('enable', True) -%}
 {%-     set comment = '' -%}
 {%-   else -%}
@@ -149,7 +148,33 @@ y
 {%-   else %}
 {{      parameter_str }}
 {%-   endif -%}
-{%- endmacro %}
+{%- endmacro -%}
+
+{#- Handle legacy configuration of services for backwards compatibility
+    by extending the services dictionary accordingly #}
+{%- if salt['pillar.get']('postfix:policyd-spf:enabled', False) %}
+{%-   do postfix_master_services_defaults.update({'policy-spf': {
+                                                    'command': 'spawn',
+                                                    'chroot': False,
+                                                    'enable': True,
+                                                    'type': 'unix',
+                                                    'unpriv': False,
+                                                    'user': 'nobody',
+                                                    'argv': '%s/bin/policyd-spf' | format(postfix.xbin_prefix)}}) %}
+{%- endif %}
+{%- if master_config.get('enable_dovecot', False) -%}
+{%-   set dovecot = master_config.get('dovecot', {} )%}
+{%-   do postfix_master_services_defaults.update({'dovecot': {
+                                                    'command': 'pipe',
+                                                    'chroot': False,
+                                                    'enable': True,
+                                                    'extras': '-d ${recipient}',
+                                                    'flags': dovecot.get('flags', 'DRhu'),
+                                                    'type': 'unix',
+                                                    'unpriv': False,
+                                                    'user': '%s:%s' | format(dovecot.get('user', 'vmail'), dovecot.get('group', 'vmail')),
+                                                    'argv': dovecot.get('argv', postfix.dovecot_deliver) }}) %}
+{%- endif %}
 # ====================================================================
 # Interfaces to non-Postfix software. Be sure to examine the manual
 # pages of the non-Postfix software to find out what options it wants.
@@ -205,13 +230,17 @@ y
 {{ extra_service('scalemail-backend', 79) }}
 #
 {{ extra_service('mailman', 79) }}
-{%- if salt['pillar.get']('postfix:policyd-spf:enabled', False) %}
+{#- Handle custom services configured as pillars by extending the services
+    dictionary for all defined services that have not been otherwise be
+    handled yet. -#}
+{%- for service in salt['pillar.get']('postfix:master_config:services', []) if not service in handled_extra_services -%}
+{%-  do postfix_master_services_defaults.update({service: salt['pillar.get']('postfix:master_config:services:%s' % (service,))}) -%}
+{%- endfor -%}
+{%- for service in postfix_master_services_defaults if not service in handled_extra_services and not service in postfix_master_services_order %}
 #
-{{ extra_service('policy-spf', False, True) }}
+{%-   if postfix_master_services_defaults[service].get('wrap', False) %}
-{%- endif %}
+{{      extra_service(service, 78) }}
-{%- if master_config.get('enable_dovecot', False) -%}
+{%-   else %}
-{%-   set dovecot = master_config.get('dovecot', {} )%}
+{{      extra_service(service) }}
-#
+{%-   endif %}
-dovecot   unix  -       n       n       -       -       pipe
+{%- endfor %}
-  flags={{ dovecot.get('flags', 'DRhu') }} user={{ dovecot.get('user', 'vmail') }}:{{ dovecot.get('group', 'vmail') }} argv={{ dovecot.get('argv', postfix.dovecot_deliver) ~ ' -d ${recipient}' }}
-{% endif -%}

postfix/services.jinja

@@ -1,5 +1,3 @@
-{%- from "postfix/map.jinja" import postfix with context -%}
-
 {#-
  #  Default Postfix master processes as defined by postfix
  #
@@ -312,17 +310,9 @@
         'user': 'list',
         'argv': '/usr/lib/mailman/bin/postfix-to-mailman.py',
     },
-    'policy-spf': {
-        'command': 'spawn',
-        'chroot': False,
-        'enable': False,
-        'type': 'unix',
-        'unpriv': False,
-        'user': 'nobody',
-        'argv': '%s/bin/policyd-spf' | format(postfix.xbin_prefix),
-    },
 } %}
 
+
 {# Service order inside the master.cf file #}
 {% set postfix_master_services_order = [
     'smtp',