#2989 added support for showing resource metadata in the web UI. Implement the corresponding functionality in the CLI, to make it easier to use metadata items like API keys.

Proposed syntax:

• coder metadata <workspace> to list all items, with sensitive values obscured by a placeholder
• coder metadata --all <workspace> to list all items
• coder metadata --get <workspace> <resource> <key> to print just the value of a specific key, without formatting or headers (for scripts)