#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/test/java/stirling/software/SPDF/config/security/database/DatabaseConfigTest.java

@@ -0,0 +1,106 @@
+package stirling.software.SPDF.config.security.database;
+
+import javax.sql.DataSource;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import stirling.software.SPDF.model.ApplicationProperties;
+import stirling.software.SPDF.model.provider.UnsupportedProviderException;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class DatabaseConfigTest {
+
+    @Mock
+    private ApplicationProperties applicationProperties;
+
+    private DatabaseConfig databaseConfig;
+
+    @BeforeEach
+    void setUp() {
+        databaseConfig = new DatabaseConfig(applicationProperties, true);
+    }
+
+    @Test
+    void testDataSource_whenRunningEEIsFalse() throws UnsupportedProviderException {
+        databaseConfig = new DatabaseConfig(applicationProperties, false);
+
+        var result = databaseConfig.dataSource();
+
+        assertInstanceOf(DataSource.class, result);
+    }
+
+    @Test
+    void testDefaultConfigurationForDataSource() throws UnsupportedProviderException {
+        var system = mock(ApplicationProperties.System.class);
+        var datasource = mock(ApplicationProperties.Datasource.class);
+
+        when(applicationProperties.getSystem()).thenReturn(system);
+        when(system.getDatasource()).thenReturn(datasource);
+        when(datasource.isEnableCustomDatabase()).thenReturn(false);
+
+        var result = databaseConfig.dataSource();
+
+        assertInstanceOf(DataSource.class, result);
+    }
+
+    @Test
+    void testCustomUrlForDataSource() throws UnsupportedProviderException {
+        var system = mock(ApplicationProperties.System.class);
+        var datasource = mock(ApplicationProperties.Datasource.class);
+
+        when(applicationProperties.getSystem()).thenReturn(system);
+        when(system.getDatasource()).thenReturn(datasource);
+        when(datasource.isEnableCustomDatabase()).thenReturn(true);
+        when(datasource.getCustomDatabaseUrl()).thenReturn("jdbc:postgresql://mockUrl");
+        when(datasource.getUsername()).thenReturn("test");
+        when(datasource.getPassword()).thenReturn("pass");
+
+        var result = databaseConfig.dataSource();
+
+        assertInstanceOf(DataSource.class, result);
+    }
+
+    @Test
+    void testCustomConfigurationForDataSource() throws UnsupportedProviderException {
+        var system = mock(ApplicationProperties.System.class);
+        var datasource = mock(ApplicationProperties.Datasource.class);
+
+        when(applicationProperties.getSystem()).thenReturn(system);
+        when(system.getDatasource()).thenReturn(datasource);
+        when(datasource.isEnableCustomDatabase()).thenReturn(true);
+        when(datasource.getCustomDatabaseUrl()).thenReturn("");
+        when(datasource.getType()).thenReturn("postgresql");
+        when(datasource.getHostName()).thenReturn("test");
+        when(datasource.getPort()).thenReturn(1234);
+        when(datasource.getName()).thenReturn("test_db");
+        when(datasource.getUsername()).thenReturn("test");
+        when(datasource.getPassword()).thenReturn("pass");
+
+        var result = databaseConfig.dataSource();
+
+        assertInstanceOf(DataSource.class, result);
+    }
+
+    @ParameterizedTest(name = "Exception thrown when the DB type [{arguments}] is not supported")
+    @ValueSource(strings = {"oracle", "mysql", "mongoDb"})
+    void exceptionThrown_whenDBTypeIsUnsupported(String datasourceType) {
+        var system = mock(ApplicationProperties.System.class);
+        var datasource = mock(ApplicationProperties.Datasource.class);
+
+        when(applicationProperties.getSystem()).thenReturn(system);
+        when(system.getDatasource()).thenReturn(datasource);
+        when(datasource.isEnableCustomDatabase()).thenReturn(true);
+        when(datasource.getCustomDatabaseUrl()).thenReturn("");
+        when(datasource.getType()).thenReturn(datasourceType);
+
+        assertThrows(UnsupportedProviderException.class, () -> databaseConfig.dataSource());
+    }
+}