#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/resources/settings.yml.template

@@ -85,6 +85,15 @@ system:
   customHTMLFiles: false # enable to have files placed in /customFiles/templates override the existing template HTML files
   tessdataDir: /usr/share/tessdata # path to the directory containing the Tessdata files. This setting is relevant for Windows systems. For Windows users, this path should be adjusted to point to the appropriate directory where the Tessdata files are stored.
   enableAnalytics: undefined # set to 'true' to enable analytics, set to 'false' to disable analytics; for enterprise users, this is set to true
+  datasource:
+    enableCustomDatabase: false # set this property to 'true' if you would like to use your own custom database configuration
+    customDatabaseUrl: jdbc:postgresql://localhost:5432/postgres # set the url for your own custom database connection. If provided, the type, hostName, port and name are not necessary and will not be used
+    username: postgres # set the database username
+    password: postgres # set the database password
+    type: postgresql # the type of the database to set (e.g. 'h2', 'postgresql')
+    hostName: localhost # the host name to use for the database url. Set to 'localhost' when running the app locally. Set to match the name of the container name of your database container when running the app on a server (Docker configuration)
+    port: 5432 # set the port number of the database. Ensure this matches the port the database is listening to
+    name: postgres # set the name of your database. Should match the name of the database you create
 
 ui:
   appName: '' # application's visible name