Deprecate usage of filter object with #before and #after
methods as around callback

Although no recognized formats use non-ASCII characters, sometimes they
can be included in the :format parameter because of invalid URLS. To
prevent encoding incompatibility errors we need to escape them before
passing the path to URI.unescape.

Closes #4379

This fixes undef `to_str' for Rack::Chunked::Body when using
caches_action + streaming on an action

Closes #5027

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Ensure that the format isn't applied twice to the cache key, else it becomes impossible to target with expire_action.

clarify which url would be used to cache a page when options are not provided to #cache_page to determine that url

elaborate on how web server configuration to check for static files on disk enables page caching to work without hitting the app server stack

It would raise undefined method controller_name for nil

Proc objects for cache_path for caches_action no longer need controller object, nor to use send when calling routing helpers

Fix Action caching bug where an action that has a non-cacheable response always renders a nil response body. It now correctly renders the response body.

Note that only GET and HTTP 200 responses can be cached.

[#6480 state:committed]
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

For example, page_cache_directory = Rails.root.join("public/cache")
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>