wallet To-Do List

Required to replace leland_srvtab:

* Write a test suite for the sanity checking in wallet-backend and
  keytab-backend.

* Add an ACL list function to display an ACL in human-readable form and
  call it from wallet-backend.

* Display ACL details when displaying objects.

* Write new files atomically in the wallet client and save backups unless
  told not to (write to file.new, link the old file to file.old, and do
  an atomic rename).

* Implement creation of srvtabs from keytabs in the wallet client.

* Add kasetkey support to the keytab object backend.

* Implement flag setting and retrieval.

* Implement support for the unchanging flag on keytabs and the backend
  remctl calls to retrieve the existing keytab.

* Implement the locked flag.

* Write the remctl configuration and finish Debian packaging of the
  wallet client and server.

Future work:

* Provide some way of getting at the history tables.  Need to get object
  and ACL history either by object or for all objects, at least.

* Log all actions to syslog.

* Write the NetDB ACL verifier.

* Write the LDAP entitlement ACL verifier.

* Write the PTS ACL verifier.

* Add a help function to wallet-backend listing the commands.

* Support displaying and possibly specifying dates in some format more
  normal than seconds since epoch.

* Log failures in the wallet-backend properly, which also requires
  catching all exceptions.

* Implement default ACL policy to allow dynamic object creation on first
  request for keytabs.

* Implement special handling for keytabs in the wallet client.

* Use the class names in the database tables when loading object and
  ACL verifier implementations.

* Error messages from ACL operations should refer to the ACLs by name
  instead of by ID.

* The ACL implementation is currently rather inefficient for ACL
  verifiers that need to maintain state (such as LDAP binds).  Now
  they're created and destroyed when verifying each ACL.  We need to
  somehow return global verifiers, probably through a factory
  implementation.

* There is a lot of duplicate code in wallet-backend.  Convert that to
  use some sort of data-driven model with argument count and flags so
  that the method calls can be written only once.

* There's a lot of code duplication in the dispatch functions in the
  Wallet::Server class.  Find a way to rewrite that so that the dispatch
  doesn't duplicate the same code patterns.

* Remove the hard-coded ADMIN ACL in the server with something more
  configurable, perhaps a global ACL table or something.

* Add the database schema version to a global table so that we can use it
  to support schema upgrades in the future.

* Write a wallet-admin program to provide an interface to things like
  database initialization and, eventually, upgrades.

* Add a function to wallet-admin to purge expired entries.  Possibly also
  check expiration before allowing anyone to get or store objects.

* Compiling kasetkey should be optional and probably not enabled by
  default.

* Add a comment field for objects that can be set by the owner.

* Add details to design-api on how to write one's own ACL verifiers and
  object implementations.

* Add readline support to the wallet client to make it easier to issue
  multiple commands.

* The keytab backend currently only supports MIT Kerberos.  Add support
  for Heimdal.

* The wallet-backend and wallet documentation share the COMMANDS section.
  Work out some means to assemble the documentation without duplicating
  content.