Security fixes, enterprise stuff and more (#3241)

# Description of Changes

Please provide a summary of the changes, including:

- Enable user to add custom JAVA ops with env JAVA_CUSTOM_OPTS
- Added support for prometheus (enabled via JAVA_CUSTOM_OPTS +
enterprise license)
- Changed settings from enterprise naming to 'Premium'
- KeygenLicense Check to support offline licenses
- Disable URL-to-PDF due to huge security bug
- Remove loud Split PDF logs
- addUsers renamed to adminSettings
- Added Usage analytics page
- Add user button to only be enabled based on total users free
- Improve Merge memory usage


Closes #(issue_number)

---

## 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.

---------

Co-authored-by: a <a>
Co-authored-by: pixeebot[bot] <104101892+pixeebot[bot]@users.noreply.github.com>
Co-authored-by: Connor Yoh <con.yoh13@gmail.com>

src/main/java/stirling/software/SPDF/service/CustomPDFDocumentFactory.java

@@ -139,7 +139,7 @@ public class CustomPDFDocumentFactory {
      * Determine the appropriate caching strategy based on file size and available memory. This
      * common method is used by both password and non-password loading paths.
      */
-    private StreamCacheCreateFunction getStreamCacheFunction(long contentSize) {
+    public StreamCacheCreateFunction getStreamCacheFunction(long contentSize) {
         long maxMemory = Runtime.getRuntime().maxMemory();
         long freeMemory = Runtime.getRuntime().freeMemory();
         long totalMemory = Runtime.getRuntime().totalMemory();

src/main/java/stirling/software/SPDF/service/PdfMetadataService.java

@@ -64,10 +64,19 @@ public class PdfMetadataService {
 
         String creator = stirlingPDFLabel;
 
-        if (applicationProperties.getEnterpriseEdition().getCustomMetadata().isAutoUpdateMetadata()
+        if (applicationProperties
+                        .getPremium()
+                        .getProFeatures()
+                        .getCustomMetadata()
+                        .isAutoUpdateMetadata()
                 && runningEE) {
 
-            creator = applicationProperties.getEnterpriseEdition().getCustomMetadata().getCreator();
+            creator =
+                    applicationProperties
+                            .getPremium()
+                            .getProFeatures()
+                            .getCustomMetadata()
+                            .getCreator();
             pdf.getDocumentInformation().setProducer(stirlingPDFLabel);
         }
 
@@ -84,9 +93,18 @@ public class PdfMetadataService {
         pdf.getDocumentInformation().setModificationDate(Calendar.getInstance());
 
         String author = pdfMetadata.getAuthor();
-        if (applicationProperties.getEnterpriseEdition().getCustomMetadata().isAutoUpdateMetadata()
+        if (applicationProperties
+                        .getPremium()
+                        .getProFeatures()
+                        .getCustomMetadata()
+                        .isAutoUpdateMetadata()
                 && runningEE) {
-            author = applicationProperties.getEnterpriseEdition().getCustomMetadata().getAuthor();
+            author =
+                    applicationProperties
+                            .getPremium()
+                            .getProFeatures()
+                            .getCustomMetadata()
+                            .getAuthor();
 
             if (userService != null) {
                 author = author.replace("username", userService.getCurrentUsername());

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

@@ -334,27 +334,40 @@ public class PostHogService {
         addIfNotEmpty(
                 properties,
                 "enterpriseEdition_enabled",
-                applicationProperties.getEnterpriseEdition().isEnabled());
-        if (applicationProperties.getEnterpriseEdition().isEnabled()) {
+                applicationProperties.getPremium().isEnabled());
+        if (applicationProperties.getPremium().isEnabled()) {
             addIfNotEmpty(
                     properties,
                     "enterpriseEdition_customMetadata_autoUpdateMetadata",
                     applicationProperties
-                            .getEnterpriseEdition()
+                            .getPremium()
+                            .getProFeatures()
                             .getCustomMetadata()
                             .isAutoUpdateMetadata());
             addIfNotEmpty(
                     properties,
                     "enterpriseEdition_customMetadata_author",
-                    applicationProperties.getEnterpriseEdition().getCustomMetadata().getAuthor());
+                    applicationProperties
+                            .getPremium()
+                            .getProFeatures()
+                            .getCustomMetadata()
+                            .getAuthor());
             addIfNotEmpty(
                     properties,
                     "enterpriseEdition_customMetadata_creator",
-                    applicationProperties.getEnterpriseEdition().getCustomMetadata().getCreator());
+                    applicationProperties
+                            .getPremium()
+                            .getProFeatures()
+                            .getCustomMetadata()
+                            .getCreator());
             addIfNotEmpty(
                     properties,
                     "enterpriseEdition_customMetadata_producer",
-                    applicationProperties.getEnterpriseEdition().getCustomMetadata().getProducer());
+                    applicationProperties
+                            .getPremium()
+                            .getProFeatures()
+                            .getCustomMetadata()
+                            .getProducer());
         }
         // Capture AutoPipeline properties
         addIfNotEmpty(