* API Revert addition of Extensible::flush_extra_methods_cache() and change to ExtensionTestState
This reverts the changes from #8465 and #8505 that relate to ExtensionTestState and the
tracking of extra methods between unit tests. The existing test from #8465 testing
overloaded Extensions after extra_methods are populated has been updated to show that you
must re-add the extension to flush the extra_methods cache if you need this behaviour.
* Revert change to InjectorTest::testExtendedExtensions
* Revert "Add failing test to show that overloaded extensions are broken in Extensible"
This reverts commit 55e79ffdfd.
* DOCS Add docs for extending extensions, and upgrade guide note to 4.3 to avoid using PHP config to do so
* NEW: Add Hierarchy::prepopulate_numchildren_cache()
API: Hierarchy::stageChildren() customisations must be applied to the base class and not include record-specific behaviour.
Adds the ability to prepopulate the cache for Hierarchy::numChildren()
in a batch.
Note that this optimisation means that stageChildren() is not called on
each record in order to calculate numChildren(). This means that the
structure of the stageChildren() query must be the same for all records
and the behaviour cannot be customised only for a subclass of the base
data class. For example, apply your customisations to SiteTree and not
a subclass.
This is an useful part of optimising the query count on tree generation.
See https://github.com/silverstripe/silverstripe-framework/issues/8379
* NEW: Add Hierarchy::prepopulateTreeDataCache()
This provides a more extensible way of preopulating caches for optimised
tree generation.
Fixes https://github.com/silverstripe/silverstripe-framework/issues/8391
