* 5.4:
[HttpClient] Various cleanups after recent changes
do not add child nodes to EmptyNode instances
consider write property visibility to decide whether a property is writable
add comment explaining why HttpClient tests are run separately
* 5.4:
[Cache] Removing null coalescing assignment operator on 5.4
[Cache] Fix storing binary keys when using pgsql
[FrameworkBundle] Add missing monolog channel tag for messenger services
[FrameworkBundle] Improve documentation about translation:extract --sort option
[VarDumper] Disable links for IntelliJ platform
[Notifier] Add bridge documentation
[HttpClient] Add hint about `timeout` and `max_duration` options
[HttpFoundation] Use separate caches for IpUtils checkIp4 and checkIp6
[FrameworkBundle] Fix wiring session.handler when handler_id is null
[FrameworkBundle] Workflow - Fix LogicException about a wrong configuration of "enabled" node
Allow arbitrary values in the "json" request option. Previously values were
limitated to arrays and objects of type JsonSerializable. This doesn't account
for scalar values and classes with public properties (which don't need to
implement JsonSerializable), all of which are perfectly acceptable arguments to
json_encode.
Kostiantyn Miakshyn