S allius/issue395 (#399)

* add button for languages setting

* build a web module for the dashboard

- load all python module from local dir
- initialize Blueprint and Babel

* set a default key for secure cookies

* add translations to docker container

* improve translation build  

- clean target erases the *.pot
- don't modify the resurt of url_for() calls
- don't translate the language description

* translate connection table, fix icon

* build relative urls for HA ingress

* fix unit test, increase coverage

app/src/web/__init__.py

@@ -0,0 +1,32 @@
+'''Quart blueprint for the proxy webserver with the dashboard
+
+Usage:
+    app = Quart(__name__, ...)
+    Web(app)
+'''
+from quart import Quart, Blueprint
+from quart_babel import Babel
+from utils import load_modules
+
+web = Blueprint('web', __name__)
+
+load_modules(__loader__)
+
+
+class Web:
+    '''Helper Class to register the Blueprint at Quart and
+    initializing Babel'''
+    def __init__(self,
+                 app: Quart,
+                 translation_directories: str | list[str],
+                 rel_urls: bool):
+        web.build_relative_urls = rel_urls
+        app.register_blueprint(web)
+
+        from .i18n import get_locale, get_tz
+        global babel
+        babel = Babel(
+            app,
+            locale_selector=get_locale,
+            timezone_selector=get_tz,
+            default_translation_directories=translation_directories)