feat: feature flags for production environment

This MR contains feature variables for released visualizations, insight sharing, sharable explorations and management of user permissions for the production environment.

libs/config/src/featureFlags.ts

+// Safely retrieve environment variable values with a default fallback
+const getEnvVariable = (key: string, defaultValue: string = 'false'): string => {
+  return import.meta.env[key] ?? defaultValue;
+};
+
 // Check if the environment is production
 const isProduction = (): boolean => {
-  return import.meta.env.GRAPHPOLARIS_VERSION === 'prod';
+  return getEnvVariable('GRAPHPOLARIS_VERSION', 'dev') === 'prod';
 };
 
 // Check if the Manage Permissions feature is enabled
 const showManagePermissions = (): boolean => {
-  return !isProduction() || (isProduction() && import.meta.env.WIP_VIEWER_PERMISSIONS === 'false');
+  return !isProduction() || (isProduction() && getEnvVariable('WIP_VIEWER_PERMISSIONS') === 'false');
 };
 
 // Check if the Insight Sharing feature is enabled
 const showInsightSharing = (): boolean => {
-  return !isProduction() || (isProduction() && import.meta.env.WIP_INSIGHT_SHARING === 'false');
+  return !isProduction() || (isProduction() && getEnvVariable('WIP_INSIGHT_SHARING') === 'false');
 };
 
 // Check if the Insight Sharing feature is enabled
 const showSharableExploration = (): boolean => {
-  return !isProduction() || (isProduction() && import.meta.env.WIP_SHARABLE_EXPLORATION === 'false');
+  return !isProduction() || (isProduction() && getEnvVariable('WIP_SHARABLE_EXPLORATION') === 'false');
 };
 
 // Utility to check if a specific visualization is released based on environment variables
 const isVisualizationReleased = (visualizationName: string): boolean => {
-  const visualizationFlag = import.meta.env[`WIP_${visualizationName.toUpperCase()}`] || 'false';
+  const visualizationFlag = getEnvVariable(`WIP_${visualizationName.toUpperCase()}`, 'false');
   return !isProduction() || (isProduction() && visualizationFlag === 'false');
 };