Respect custom username/password properties

Fix a bug in `DataSourceInitializationConfiguration` and in
`R2dbcInitializationConfiguration` that was stopping
custom username/password properties from being applied.

Fixes gh-26676

Author: philwebb

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/sql/init/DataSourceInitializationConfiguration.java

@@ -44,7 +44,7 @@ DataSourceScriptDatabaseInitializer dataSourceScriptDatabaseInitializer(DataSour
 
 	private static DataSource determineDataSource(DataSource dataSource, String username, String password) {
 		if (StringUtils.hasText(username) && StringUtils.hasText(password)) {
-			DataSourceBuilder.derivedFrom(dataSource).username(username).password(password)
+			return DataSourceBuilder.derivedFrom(dataSource).username(username).password(password)
 					.type(SimpleDriverDataSource.class).build();
 		}
 		return dataSource;

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/sql/init/R2dbcInitializationConfiguration.java

@@ -50,7 +50,7 @@ R2dbcScriptDatabaseInitializer r2dbcScriptDatabaseInitializer(ConnectionFactory
 	private static ConnectionFactory determineConnectionFactory(ConnectionFactory connectionFactory, String username,
 			String password) {
 		if (StringUtils.hasText(username) && StringUtils.hasText(password)) {
-			ConnectionFactoryBuilder.derivefrom(connectionFactory).username(username).password(password).build();
+			return ConnectionFactoryBuilder.derivefrom(connectionFactory).username(username).password(password).build();
 		}
 		return connectionFactory;
 	}