Description

As a pack user it would be nice to have commands to manage the registries in the config file.

Proposed solution

• pack list-buildpack-registry - a new command that will list all the [[registries]] config in .pack/config.toml.
• pack add-buildpack-registry - a new command that will add to the [[registries]] config in .pack/config.toml.
• pack remove-buildpack-registry - a new command that will remove a registry from the [[registries]] config in .pack/config.toml.
• pack set-buildpack-registry - a new command that will mutate the default-registry config in .pack/config.toml.

For more details on what the data structure of the .pack/config.toml see RFC #44.

Additional Refactor/Clean-up

add-buildpack-registry -> add-registry
list-buildpack-registry -> list-registries

Additional context

• This feature should be documented somewhere

• These commands should be hidden via experimental config option.