#2270: External DB Support (#2457)

# Description

External DB support for Stirling PDF. You can now choose between the
default H2 or PostgreSQL by setting the new `enableCustomDatabase`
property to `true` or `false`.

To enable your own custom (PostgreSQL) database:
- Set `enableCustomDatabase` to `true`
- Add your database url to `customDatabaseUrl`
- Set your `username` and `password`

Closes #2270 

## Checklist

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have performed a self-review of my own code
- [x] I have attached images of the change if it is UI based
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] If my code has heavily changed functionality I have updated
relevant docs on [Stirling-PDFs doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
- [x] My changes generate no new warnings
- [x] 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)

src/main/java/stirling/software/SPDF/EE/LicenseKeyChecker.java

@@ -18,7 +18,7 @@ public class LicenseKeyChecker {
 
     private final ApplicationProperties applicationProperties;
 
-    private boolean enterpriseEnbaledResult = false;
+    private boolean enterpriseEnabledResult = false;
 
     @Autowired
     public LicenseKeyChecker(
@@ -35,12 +35,12 @@ public class LicenseKeyChecker {
 
     private void checkLicense() {
         if (!applicationProperties.getEnterpriseEdition().isEnabled()) {
-            enterpriseEnbaledResult = false;
+            enterpriseEnabledResult = false;
         } else {
-            enterpriseEnbaledResult =
+            enterpriseEnabledResult =
                     licenseService.verifyLicense(
                             applicationProperties.getEnterpriseEdition().getKey());
-            if (enterpriseEnbaledResult) {
+            if (enterpriseEnabledResult) {
                 log.info("License key is valid.");
             } else {
                 log.info("License key is invalid.");
@@ -55,6 +55,6 @@ public class LicenseKeyChecker {
     }
 
     public boolean getEnterpriseEnabledResult() {
-        return enterpriseEnbaledResult;
+        return enterpriseEnabledResult;
     }
 }