Enhancement: cache management - flush, inspect, remove individually

[robbieaverill]

• cache:list: list all cache IDs as well as some information about them
• cache:dump: Dump the contents of everything in the cache, or by ID
• cache:flush: Clear the entire cache manifest
• cache:view: View the contents of specific cache entries by key This can be incorporated as an argument of cache:dump
• cache:remove Remove specific cache entries by key

I'm not sure that the ConfigManifest will actually let us do these:

• cache:enable: Enable the global cache (if disabled)
• cache:disable: Disable the global cache (if enabled)

[robbieaverill]

I've rejigged the requirements for this after an initial investigation. I don't think enable and disable would be doable with the way the manifest is loaded on every request.

[robbieaverill]

SilverStripe's cache management is still fairly singular. You can configure different cache services via injector, which is something that we could surface with a command like this (e.g. cache:list lists all CacheInterface implementations registered under Injector, with their cache status, TTL etc), and we could allow each of them to be individually flushed.

I expect in future that more granular cache entry separation and handling might become more important in core, so this could be a useful command to add proactively.