Instead of providing a configuration option to set the hash function,
switch to SHA-1 for new apps and allow upgrading apps to opt in later
via `new_framework_defaults_5_2.rb`.
Having collection caching that wraps templates and automatically tries
to infer if they are cachable proved to be too much of a hassle.
We'd rather have it be something you explicitly turn on.
This removes much of the code and docs to explain the previous automatic
behavior.
This change also removes scoped cache keys and passing cache_options.
This moves digest calculation cache on to the details key object.
Before, the digest cache was a class level ivar, and one of the keys was
the hash value of the details key object:
13c4cc3b5a/actionview/lib/action_view/digestor.rb (L28)
An object's hash value is not unique, so it's possible for this cache
key to produce colliding keys with no resolution. This commit move
cache on to the details key object itself, so we know that the digests
are always unique per details key object.
Avoid computing the same fragment digest many times when looping over templates.
The cache is cleared on every request so template changes are still picked up.
