wireguard: Add button for direct APK download

**clients.py**
- allow download type for mobile os

**manifest.py**
- add entry for apk download

**plinth/templates/clients.html**
- add logic to show button for apk download

**themes > icons**
- add icon for android

source: https://www.wireguard.com/install/

Signed-off-by: Frederico Gomes <fredericojfgomes@gmail.com>
[sunil: Minor indentation]
[sunil: Refactor logic to eliminate packages from Desktop clients list]
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/clients.py

@@ -116,7 +116,7 @@ def _validate_platform_package(platform):
 
 def _validate_platform_download(platform):
     """Validate a platform of type download."""
-    assert platform['os'] in enum_values(Desktop_OS)
+    assert platform['os'] in enum_values(Desktop_OS) + enum_values(Mobile_OS)
     assert isinstance(platform['url'], (str, Promise))
 
 

plinth/modules/wireguard/manifest.py

@@ -25,6 +25,11 @@ clients = [{
         'type': 'package',
         'format': 'deb',
         'name': 'wireguard'
+    }, {
+        'type': 'download',
+        'os': 'android',
+        'url': ('https://www.wireguard.com/'
+                'install/#android-play-store-direct-apk-file')
     }, {
         'type': 'store',
         'os': 'android',

plinth/templates/clients.html

@@ -45,6 +45,7 @@
             <td>
               {% for platform in client.platforms %}
                 {% if platform.type == 'download' %}
+                  {% if platform.os == 'gnu-linux' or platform.os == 'macos' or platform.os == 'windows' %}
                     <a class="btn btn-default" href="{{ platform.url }}" role="button">
                       <span>
                         {% with 'theme/icons/'|add:platform.os|add:'.png' as icon %}
@@ -60,6 +61,7 @@
                       </span>
                     </a>
                   {% endif %}
+                {% endif %}
               {% endfor %}
             </td>
           </tr>
@@ -75,6 +77,16 @@
             <td>{{ client.name }}</td>
             <td>
               {% for platform in client.platforms %}
+                {% if platform.type == 'download' and platform.os == 'android' %}
+                  <a class="btn btn-default" href="{{ platform.url }}" role="button">
+                    <span>
+                      {% with 'theme/icons/'|add:platform.os|add:'.png' as icon %}
+                        <img class="client-icon" src="{% static icon %}" />
+                        {% trans 'Android APK' %}
+                      {% endwith %}
+                    </span>
+                  </a>
+                {% endif %}
                 {% if platform.type == 'store' and platform.os == 'android' or platform.os == 'ios' %}
                   <a class="btn btn-default" href="{{ platform.url }}" role="button">
                     <span>