M5: end-to-end test matrix and CI

- tests/integration/roundtrip.sh: key, kit code and confirmation,
  location, full and unchanged incremental backup, restore new-folder and
  replace (files identical, extra file in the trash), database dump and
  restore, retention, trash and restore from trash, no files_external
  errors in the log
- tests/integration/matrix.sh: fresh Nextcloud per version and database
  (SQLite, MariaDB, PostgreSQL), removes only its own containers and
  their volumes; locally green on NC32 and NC35 with all three databases
- GitHub Actions: unit tests on PHP 8.2-8.4, round trip on NC32-35 x
  SQLite/MariaDB/PostgreSQL

Fixes found by the matrix:
- files_external is no longer booted when it is disabled: only its
  classes are loaded and a private BackendService gets its backends from
  its Application class (booting registered its mount provider, which
  failed on installations where its tables were never created)
- SQLite: the database file is excluded from the file backup (it is
  covered by the logical dump and copying the live file is inconsistent)
- occ backup:key:confirm accepts --code and --confirm for scripts

lib/Command/KeyConfirm.php

@@ -28,7 +28,9 @@ class KeyConfirm extends Command {
 	protected function configure(): void {
 		$this->setName('backup:key:confirm')
 			->setDescription('Confirm that the recovery kit is stored safely (required before the first backup)')
-			->addOption('user', 'u', InputOption::VALUE_REQUIRED, 'Admin user id recorded with the confirmation', 'occ');
+			->addOption('user', 'u', InputOption::VALUE_REQUIRED, 'Admin user id recorded with the confirmation', 'occ')
+			->addOption('code', null, InputOption::VALUE_REQUIRED, 'Confirmation code from the kit file (for scripts; asked otherwise)')
+			->addOption('confirm', null, InputOption::VALUE_REQUIRED, 'The confirmation phrase "' . self::CONFIRMATION . '" (for scripts; asked otherwise)');
 	}
 
 	protected function execute(InputInterface $input, OutputInterface $output): int {
@@ -40,12 +42,12 @@ class KeyConfirm extends Command {
 		$output->writeln('');
 		$output->writeln(wordwrap(self::STATEMENT, 78));
 		$output->writeln('');
-		$code = (string)$this->getHelper('question')->ask($input, $output, new Question('Confirmation code from the recovery kit file ("confirmation_code"): '));
+		$code = $input->getOption('code') ?? (string)$this->getHelper('question')->ask($input, $output, new Question('Confirmation code from the recovery kit file ("confirmation_code"): '));
 		if (!$this->keys->checkKitCode($code)) {
 			$output->writeln('<error>That code does not match the current recovery kit (download it with occ backup:key:kit first).</error>');
 			return 1;
 		}
-		$answer = (string)$this->getHelper('question')->ask($input, $output, new Question('Type "' . self::CONFIRMATION . '" to proceed: '));
+		$answer = $input->getOption('confirm') ?? (string)$this->getHelper('question')->ask($input, $output, new Question('Type "' . self::CONFIRMATION . '" to proceed: '));
 		if (trim($answer) !== self::CONFIRMATION) {
 			$output->writeln('<error>Not confirmed.</error>');
 			return 1;