Allow authentication header to not have to specify 'token=' key.

Fixes: https://github.com/rails/rails/issues/17108.
Correct test description for large integer test
[Testing guide] Use "Fixtures API" instead of "fixture api".
[Testing guide] Using "Fixtures API" consistently

- In guides, "API" is used consistently instead of "api".
- Reason behind replacing "fixtures API" to "Fixtures API" is because
  here we are referring to the concept of "fixtures". In other places in
  the guide "fixture" OR "fixtures" is referred to the single or
  multiple instances of test data.
- This is also followup of https://github.com/rails/docrails/commit/aa9d1332b20305dd860b21a7ada06c5252bebad5#commitcomment-8497376.
Allow habtm class_name option to be consistent with other associations
Introduce test to demonstrate regression caused by da99a2a2
Revert "PERF: optimise type lookup to avoid invoking procs"

This reverts commit da99a2a2982d35f670ad9647463e09bfe9032b70.
That last test was incorrect... ☕
Remove bullet point to unwritten/unreferenced section
Merge pull request #17677 from StevenNunez/patch-1

Remove bullet point to unwritten/unreferenced section
Add tests for `TypeMap#fetch` and push up to `TypeMap`

It doesn't make sense for the subclass to implement this method, and not
have it on the parent. We can also DRY up the implementation of
`#lookup` to be defined in terms of fetch, which will give us a single
point of entry
Reintroduce cache with tests
Fix shell quote on the release task
Merge pull request #17575 from shikshachauhan/make-habtm-consistent

Allow class_name option in habtm to be consistent with other association...
Some valid block calls in templates caused syntax errors

Now ActionView accepts <%= foo(){ %> and <%= foo()do %> :golf:
PERF: avoid string allocations
Explain that default_scope also influences update_all

This was not explicitly stated before and I needed to try it out to be
certain. A little explicit statement in the API docs might help here.
synchronize code and docs for `timestamps` and `add_timestamps`.

This makes the following changes:
  * warn if `:null` is not passed to `add_timestamps`
  * `timestamps` method docs link to `add_timestamps` docs
  * explain where additional options go
  * adjust examples to include `null: false` (to prevent deprecation warnings)
[CI SKIP] Improvements to Active Job guide.
Merge pull request #17669 from SamSaffron/optimise_memory

PERF: avoid string allocations