Multi module refactor (#3640)

# Description of Changes

Migrated Stirling PDF to a multi-module structure:

* Introduced new `:stirling-pdf` module
* Moved all the core logic and features of Stirling PDF into
`:stirling-pdf`
* Updated paths of jobs and scripts

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

common/src/main/java/stirling/software/common/configuration/AppConfig.java

@@ -1,5 +1,7 @@
 package stirling.software.common.configuration;
 
+import io.github.pixee.security.SystemCommand;
+import jakarta.annotation.PostConstruct;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -149,12 +151,12 @@ public class AppConfig {
 
     @Bean(name = "activeSecurity")
     public boolean activeSecurity() {
-        String additionalFeaturesOff = env.getProperty("DISABLE_ADDITIONAL_FEATURES");
+        String disableAdditionalFeatures = env.getProperty("DISABLE_ADDITIONAL_FEATURES");
 
-        if (additionalFeaturesOff != null) {
+        if (disableAdditionalFeatures != null) {
             // DISABLE_ADDITIONAL_FEATURES=true means security OFF, so return false
             // DISABLE_ADDITIONAL_FEATURES=false means security ON, so return true
-            return !Boolean.parseBoolean(additionalFeaturesOff);
+            return !Boolean.parseBoolean(disableAdditionalFeatures);
         }
 
         return env.getProperty("DOCKER_ENABLE_SECURITY", Boolean.class, true);
@@ -164,7 +166,7 @@ public class AppConfig {
     @ConditionalOnMissingClass(
             "stirling.software.proprietary.security.configuration.SecurityConfiguration")
     public boolean missingActiveSecurity() {
-        return false;
+        return true;
     }
 
     @Bean(name = "directoryFilter")

common/src/main/java/stirling/software/common/model/ApplicationProperties.java

@@ -344,10 +344,10 @@ public class ApplicationProperties {
         @Override
         public String toString() {
             return """
-                    Driver {
-                      driverName='%s'
-                    }
-                    """
+                Driver {
+                  driverName='%s'
+                }
+                """
                     .formatted(driverName);
         }
     }

common/src/main/java/stirling/software/common/service/PostHogService.java

@@ -208,7 +208,7 @@ public class PostHogService {
 
         // New environment variables
         dockerMetrics.put("version_tag", System.getenv("VERSION_TAG"));
-        dockerMetrics.put("without_enhanced_features", System.getenv("WITHOUT_ENHANCED_FEATURES"));
+        dockerMetrics.put("additional_features_off", System.getenv("ADDITIONAL_FEATURES_OFF"));
         dockerMetrics.put("fat_docker", System.getenv("FAT_DOCKER"));
 
         return dockerMetrics;

common/src/main/java/stirling/software/common/util/ValidationUtil.java

@@ -0,0 +1,14 @@
+package stirling.software.common.util;
+
+import java.util.Collection;
+
+public class ValidationUtil {
+
+    public static boolean isStringEmpty(String input) {
+        return input == null || input.isBlank();
+    }
+
+    public static boolean isCollectionEmpty(Collection<String> input) {
+        return input == null || input.isEmpty();
+    }
+}