[Request]: Minimal feature set for common defaults management.

[jglogan]

Feature or enhancement request details

As a container user, I can use a common set of CLI commands to get names, descriptions and values for application defaults, as well as set and clear default values, so that I can adapt default behavior to my needs.

Currently defaults management is scattered about, using varying verbs.

Bulk load/merge/extraction of defaults is out of scope and can be handled in follow-up issues.

Code of Conduct

• I agree to follow this project's Code of Conduct

[jglogan]

An example of the scattering today:

% container registry default --help
Warning! Running debug build. Performance may be degraded.
OVERVIEW: Manage the default image registry

USAGE: container registry default <subcommand>

OPTIONS:
  --version               Show the version.
  -h, --help              Show help information.

SUBCOMMANDS:
  set                     Set the default registry
  unset, clear            Unset the default registry
  inspect                 Display the default registry domain

  See 'container help registry default <subcommand>' for detailed help.

% container system dns default --help
Warning! Running debug build. Performance may be degraded.
OVERVIEW: Set or unset the default local DNS domain

USAGE: container system dns default <subcommand>

OPTIONS:
  --version               Show the version.
  -h, --help              Show help information.

SUBCOMMANDS:
  set                     Set the default local DNS domain
  unset, clear            Unset the default local DNS domain
  inspect                 Display the default local DNS domain

  See 'container help system dns default <subcommand>' for detailed help.

[jglogan]

Plan

• Relocate ClientDefaults.swift to something like ApplicationDefaults or SystemDefaults in the ContainerPersistence target, to make defaults management accessible to client and server code without the heavyweight coupling to ContainerClient.
• Coalesce core properties under system property subcommand, adding property descriptions. Replace scattered defaults subcommands with system property. #604
• Update user documentation to reference the new commands. Replace scattered defaults subcommands with system property. #604