test: move structure.yml to tests and remove cst volume leak

container-structure-test left one anonymous volume per test container.
tests/structure.py runs it with --save and removes the new containers
with their volumes afterwards.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/required-features.txt

@@ -1,18 +0,0 @@
-# Optional features that MUST be present in the built image.
-#
-# One gate name per line. Known gates and the pull request that introduces
-# them (see test/features.sh):
-#
-#   stream       stream backups via RESTIC_STREAM            PR #109
-#   docker-cli   docker cli inside the container             PR #99
-#   bash         bash for pre/post hooks                     PR #99
-#   msmtp        mail relay via msmtp                        PR #84
-#
-# While a gate is NOT listed here its tests are reported as SKIP when the
-# feature is absent, so an open pull request does not turn master red.
-#
-# When you merge a feature, add its gate name below. From then on the feature
-# tests are mandatory and a feature that silently disappears from the image
-# fails the build.
-#
-# Empty on purpose: master currently ships none of the optional features.

test/structure.yml

@@ -1,64 +0,0 @@
-schemaVersion: '2.0.0'
-
-# Structural contract of the image. Everything asserted here is something a
-# user can reach from outside: a binary they call from a hook, a path they
-# mount, or the way the container is started.
-
-commandTests:
-  - name: 'restic is installed'
-    command: 'restic'
-    args: ['version']
-    expectedOutput: ['restic \d+\.\d+\.\d+.*']
-  - name: 'rclone is installed'
-    command: 'rclone'
-    args: ['--version']
-    expectedOutput: ['rclone v.*']
-  - name: 'curl is installed, used for Teams notifications'
-    command: 'curl'
-    args: ['--version']
-    expectedOutput: ['curl \d+\..*']
-  - name: 'mail is installed, used for mail notifications'
-    command: 'sh'
-    args: ['-c', 'command -v mail']
-    expectedOutput: ['/usr/bin/mail']
-  - name: 'crond is available'
-    command: 'sh'
-    args: ['-c', 'command -v crond']
-    expectedOutput: ['/usr/sbin/crond']
-  - name: 'flock is available, the cron jobs depend on it'
-    command: 'sh'
-    args: ['-c', 'test -x /usr/bin/flock && echo ok']
-    expectedOutput: ['ok']
-
-fileExistenceTests:
-  - name: 'backup script'
-    path: '/bin/backup'
-    shouldExist: true
-    permissions: '-rwxr-xr-x'
-  - name: 'check script'
-    path: '/bin/check'
-    shouldExist: true
-    permissions: '-rwxr-xr-x'
-  - name: 'entrypoint'
-    path: '/entry.sh'
-    shouldExist: true
-    permissions: '-rwxr-xr-x'
-  - name: 'default repository mount point'
-    path: '/mnt/restic'
-    shouldExist: true
-  - name: 'cron log file'
-    path: '/var/log/cron.log'
-    shouldExist: true
-  - name: 'crontab directory'
-    path: '/var/spool/cron/crontabs'
-    shouldExist: true
-
-metadataTest:
-  volumes: ['/data']
-  entrypoint: ['/entry.sh']
-  cmd: ['tail', '-fn0', '/var/log/cron.log']
-  envVars:
-    - key: 'RESTIC_REPOSITORY'
-      value: '/mnt/restic'
-    - key: 'BACKUP_CRON'
-      value: '0 */6 * * *'