Add support for empty password in bitnami/postgresql

See gh-43771

Signed-off-by: He Zean <realhezean@gmail.com>

spring-boot-project/spring-boot-docker-compose/src/test/java/org/springframework/boot/docker/compose/service/connection/postgres/PostgresEnvironmentTests.java

@@ -93,6 +93,12 @@ class PostgresEnvironmentTests {
 		assertThat(environment.getPassword()).isNull();
 	}
 
+	@Test
+	void getPasswordWhenHasNoPasswordAndAllowEmptyPassword() {
+		PostgresEnvironment environment = new PostgresEnvironment(Map.of("ALLOW_EMPTY_PASSWORD", "yes"));
+		assertThat(environment.getPassword()).isEmpty();
+	}
+
 	@Test
 	void getDatabaseWhenNoPostgresDbOrPostgresUser() {
 		PostgresEnvironment environment = new PostgresEnvironment(Map.of("POSTGRES_PASSWORD", "secret"));