Add CLI tools to manage the masking proxy database

Depends on !1111 (merged)

TODO:

• Create a request and get its slug (sysdamin readable) and uuid (we can publish):

  `swh storage masking record-request [-m REASON] SLUG`

• Change object masking states:

  cat SWHIDS | swh storage masking update-state [-f FILE] [-m MESSAGE] SLUG NEW_STATE

• See masked objects:

  swh storage masking request-status $SLUG

• See history:

  swh storage masking request-history $SLUG

• Mask an origin and everyone of its objects: ( swh-alter!22 (merged))

  swh alter list-candidates --(no-)check-references <SWHID|ORIGIN>… → output swhids on stdout

• See object status:

  swh storage masking object-status <SWHID>… or stdin → is it masked and by which decision(s)

• Delete a decision

  swh storage masking clear-request $SLUG $MESSAGE → remove all objects but keep the decision and history