We should assert that routes will not be recognized if the verbs do
not match.

Follow up to rails#15321

Instead of duplicating the routes, we will first match the HEAD request to
HEAD routes. If no match is found, we will then map the HEAD request to
GET routes.

[ci skip] 4.2 release notes grammar fix

Enable gzip compression by default

If someone is using ActionDispatch::Static to serve assets and makes it past the `match?` then the file exists on disk and it will be served. This PR adds in logic that checks to see if the file being served is already compressed (via gzip) and on disk, if it is it will be served as long as the client can handle gzip encoding. If not, then a non gzip file will be served.

This additional logic slows down an individual asset request but should speed up the consumer experience as compressed files are served and production applications should be delivered with a CDN. This PR allows a CDN to cache a gzip file by setting the `Vary` header appropriately. In net this should speed up a production application that are using Rails as an origin for a CDN. Non-asset request speed is not affected in this PR.

[ci skip] Fixing spelling typo in testing guide.

Remove cached attributes from Configuring guide [ci skip]

This was removed in #15429

Remove ActiveRecord config instructions for active_record.attribute_types_cached_by_default, which was removed in https://github.com/rails/rails/commit/66736c8e50585

It was soft removed at 03035d69

[ci skip] Fix Active Job grammar in api docs

[ci skip] add doc for STEP in migration

[ci skip] Added documentation for has_many scope parameter

[ci skip] correct docs about the migration generation

[ci skip] Fix typos/grammar in Active Job guide

Point release notes to stable branch for list of commits. [ci skip]

Point release notes to stable branch for list of commits. [ci skip]

[Rdoc] Make clear that we are sending an AR object [ci skip]

has_many :through with dynamic condition merging

Fix typo in rdoc [ci skip]

Deprecated ActionMailer .deliver and updated ActionMailer / ActiveJob docs/guide

Require ActiveJob in case a skip_xxx option is given

Change position of require active_job

[ci skip] Format pass of Active Job Basics guide.

Zero has one digit, but Math.log10(0) returns -Infinity. The method
needs to special-case zero.

The patch adds a regression test that is not clearly related to the
underlying issue because digit_count is private and has no coverage.
Gray area.

This bug was uncovered by 60062cf3.

don't log errors when all is fine