help: Move custom static file handling into app from central place

Tests performed:

- Print the calls to _mount_static_directory() before and after the changes.
They should print the same.

- With English as the preferred language, visit the user manual. Images should
be visible. Visit MediaWiki manual page with learn more link in MediaWiki.
Images should be visible.

- Repeat with Spanish as the preferred language.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/modules/help/__init__.py

@@ -3,10 +3,12 @@
 FreedomBox app for help pages.
 """
 
+import os
+
 from django.utils.translation import ugettext_lazy as _
 
 from plinth import app as app_module
-from plinth import menu
+from plinth import cfg, menu, web_server
 
 version = 1
 
@@ -51,6 +53,17 @@ class HelpApp(app_module.App):
                               order=100)
         self.add(menu_item)
 
+        directory_map = {}
+        langs = os.listdir(os.path.join(cfg.doc_dir, 'manual'))
+        for lang in langs:
+            manual_dir = os.path.join(cfg.doc_dir, 'manual', lang, 'images')
+            manual_url = f'/help/manual/{lang}/images'
+            directory_map[manual_url] = manual_dir
+
+        static_files = web_server.StaticFiles('static-files-help',
+                                              directory_map)
+        self.add(static_files)
+
 
 def init():
     """Initialize the Help module"""

plinth/web_server.py

@@ -56,13 +56,6 @@ def init():
 
     _mount_static_directory('/usr/share/javascript', '/javascript')
 
-    langs = os.listdir(os.path.join(cfg.doc_dir, 'manual'))
-    for lang in langs:
-        manual_dir = os.path.join(cfg.doc_dir, 'manual', lang, 'images')
-        manual_url = '/'.join([cfg.server_dir, f'help/manual/{lang}/images']) \
-                        .replace('//', '/')
-        _mount_static_directory(manual_dir, manual_url)
-
     for module_name, module in module_loader.loaded_modules.items():
         module_path = os.path.dirname(module.__file__)
         static_dir = os.path.join(module_path, 'static')