Warn and/or protect against multiple parties updating HttpResources

[rstoyanchev]

Global resources are very convenient and work transparently as long as all parties participate without customization. If multiple parties try to change the global resources via HttpResources, it should continue to work, as long as HttpResources.get() is used to access the resources, but the later changes would silently override the earlier ones, which could be tricky to find out and an unwelcome surprise.

In the very least consider adding WARN level log messages to warn that the global settings have been explicitly set (if resources were not yet created), and likewise warn that global settings have set again, overriding previous customization (if already created).

Possibly consider an even stronger measure such as to requiring an explicit reset or shutdown before settings can be changed again, in order to avoid silent overrides.

[violetagg]

In the very least consider adding WARN level log messages to warn that the global settings have been explicitly set (if resources were not yet created), and likewise warn that global settings have set again, overriding previous customization (if already created).

With #452 a WARN message is added for both cases (create/update)

Possibly consider an even stronger measure such as to requiring an explicit reset or shutdown before settings can be changed again, in order to avoid silent overrides.

The current implementation disposes the previous loops/pools when updated
https://github.com/reactor/reactor-netty/blob/0.7.x/src/main/java/reactor/ipc/netty/tcp/TcpResources.java#L222