Ignore private pragma

[nspragg]

Determining whether a response should be cached, involves checking no-store and private. See

Is some cases, not caching a response because private is present in the cache control header may be undesirable. private is used to indicate a response is for a single user and not be to added to a shared cache. e.g mediaselector does this.

Therefore, allow private to be ignored with a configuration option.

[niklasR]

Sounds good to me 👍

[andymsuk]

And me 👍