#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/config/security/oauth2/CustomOAuth2AuthenticationSuccessHandler.java

@@ -1,6 +1,7 @@
 package stirling.software.SPDF.config.security.oauth2;
 
 import java.io.IOException;
+import java.sql.SQLException;
 
 import org.springframework.security.authentication.LockedException;
 import org.springframework.security.core.Authentication;
@@ -18,6 +19,7 @@ import stirling.software.SPDF.config.security.UserService;
 import stirling.software.SPDF.model.ApplicationProperties;
 import stirling.software.SPDF.model.ApplicationProperties.Security.OAUTH2;
 import stirling.software.SPDF.model.AuthenticationType;
+import stirling.software.SPDF.model.provider.UnsupportedProviderException;
 import stirling.software.SPDF.utils.RequestUriUtils;
 
 public class CustomOAuth2AuthenticationSuccessHandler
@@ -97,10 +99,8 @@ public class CustomOAuth2AuthenticationSuccessHandler
                     userService.processSSOPostLogin(username, oAuth.getAutoCreateUser());
                 }
                 response.sendRedirect(contextPath + "/");
-                return;
-            } catch (IllegalArgumentException e) {
+            } catch (IllegalArgumentException | SQLException | UnsupportedProviderException e) {
                 response.sendRedirect(contextPath + "/logout?invalidUsername=true");
-                return;
             }
         }
     }