Fix some sass deprecation warnings.

Silence the rest, as it originates from bootstrap 5, which we do not have control over.

Keep an @import for bootstrap in the application.scss as bootstrap is
not compatible with newer sass.

Also switch sass-loader to use the modern Dart Sass JavaScript API instead of the legacy one.

This resolves Module Warning (from ./node_modules/sass-loader/dist/cjs.js):
              Deprecation The legacy JS API is deprecated and will be removed in Dart Sass 2.0.0.

              More info: https://sass-lang.com/d/legacy-js-api

Author: johanib

public/scss/application.scss

@@ -1,9 +1,10 @@
 @charset "utf-8";
 
-@import "vars";
-@import "authentication";
-@import "wayg";
-@import "~bootstrap/scss/bootstrap";
+@use "vars" as *;
+@use "authentication";
+@use "wayg";
+
+@import "../../node_modules/bootstrap/scss/bootstrap";
 
 body {
   background-color: $gray-200;

public/scss/authentication.scss

@@ -1,3 +1,5 @@
+@use "vars" as *;
+
 body.authentication {
 
   .container.authentication {

webpack.config.js

@@ -9,10 +9,13 @@ Encore
     .enableTypeScriptLoader()
     .enableLessLoader()
     .enableSassLoader(options => {
+        options.api = 'modern';
         options.sassOptions = {
             outputStyle: 'expanded',
             includePaths: ['public'],
+            silenceDeprecations: ["import", "color-functions", "global-builtin"]
         };
+        options.webpackImporter = false;
     })
 
     .addStyleEntry('global', [