mention controller test base class in testing guide. [ci skip]
Allow attaching to AS::Notifications namespace up front

Before, you were required to attach *after* adding the methods to the
class, since the attachment process needed the methods to be present.

With this change, any new method will also be attached to the configured
namespace.
Fix: Remove broken link on rails 3 guide

As raised in https://github.com/rails/rails/issues/12300
[ci skip]
Merge pull request #12299 from hitendrasingh/code_refactor

DRYing up method_missing code; Initializing Codepoint object with default values
Merge pull request #12285 from dasch/dasch/allow-attaching-up-front

Allow attaching to AS::Notifications namespace up front
exposing target records on the preloader
do not access internal data structures
generate fewer objects when grouping
extract exception raising, clean up group_by statement
just read the attribute rather than `send`ing
lhs preload is always a single preload, so just preload one
Merge pull request #11452 from dasch/dasch/details-in-digestor-cache-key

Bust the template digest cache key when details are changed
stop depending on preloader interals so we can create fewer preloader
objects
the hash should only ever be length one, so decompose it
Merge pull request #12301 from Gazler/guide_3_0_release_notes_broken_link

Documentation Fix: Remove broken link on rails 3 guide

Closes #12300
push `run` up to preload
push running the preloaders up
access preloaders independently of model mutations
fix method name
split up construction and mutation