feat(map): allow jinja processing of parameters values

We allow the load of `.jinja` files to circumvent yamllint errors when
using Jinja in YAML files.

We load:

- `defaults.yaml.jinja` after `defaults.yaml`
- `post_map.yaml.jinja` at the end

openvpn/libmapstack.jinja

@@ -203,16 +203,15 @@
             | join("/") %}
 
 {%-         for yaml_name in yaml_names %}
-{#-           Make sure to have a `.yaml` extension #}
-{#-           Use `.rpartition` to strip last `.yaml` in `dir.yaml/file.yaml` #}
+{#-           Append a `.yaml` extension except if already present or for `.jinja` #}
+{%-           if yaml_name.rpartition(".")[2] not in ["yaml", "jinja"] %}
+{%-             set yaml_name = yaml_name ~ ".yaml" %}
+{%-           endif %}
+
 {%-           set yaml_filename = [
                 yaml_dir.rstrip("/"),
-                yaml_name.rpartition(".yaml")
-                | reject("equalto", ".yaml")
-                | join
-                ~ ".yaml"
+                yaml_name
               ]
-              | select
               | join("/") %}
 
 {%-           do salt["log.debug"](

openvpn/map.jinja

@@ -37,7 +37,14 @@
     ) %}
 
 {#- Load formula parameters values #}
-{%- set _formula_matchers = ["defaults.yaml"] + map_sources %}
+{%- set _formula_matchers =
+      [
+        "defaults.yaml",
+        "defaults.yaml.jinja",
+      ]
+      + map_sources
+      + ["post_map.yaml.jinja"] %}
+
 {%- set _formula_settings = mapstack(
       matchers=_formula_matchers,
       dirs=[formula_param_dir],

openvpn/parameters/defaults.yaml

@@ -1,4 +1,3 @@
-# yamllint disable-file
 # -*- coding: utf-8 -*-
 # vim: ft=yaml
 ---
@@ -14,7 +13,7 @@ values:
   group: nobody
   # None, will default to 'user'
   log_user: ~
-  multi_services: {{ salt['grains.has_value']('systemd') }}
+  multi_services: false
   pkgs: ['openvpn']
   service: openvpn
   service_function: running

openvpn/parameters/defaults.yaml.jinja

@@ -0,0 +1,15 @@
+{#- -*- coding: utf-8 -*- #}
+{#- vim: ft=jinja #}
+{#-
+    Setup variables after loading `defaults.yaml`.
+
+    This jinja2 file must return a valid `map.jinja` YAML which will
+    be merged into `defaults.yaml`.
+
+    If you do not need to provide calculated defaults, you can remove
+    this file or provide at least an empty dict, e.g.  values: {}
+#}
+---
+values:
+  multi_services: {{ salt['grains.has_value']('systemd') }}
+...