Add 'pipeline' storage "class" for more readable configurations.
This would allow writing configurations like:
storage:
cls: pipeline
steps:
- cls: filter
- cls: buffer
- cls: remote
url: http://swh-storage:5002/or
storage:
cls: filter
storage:
cls: buffer
storage:
cls: remote
url: http://swh-storage:5002/instead of:
storage:
cls: filter
args:
storage:
cls: buffer
args:
storage:
cls: remote
args:
url: http://swh-storage:5002/