Immutable locking config

[seba-aln]

feat: Optionally immutable config.

Option to lock PNConfiguration mutability. Note that mutable config will be deprecated in future major releases

[wkal-pubnub]

if, as a user, I wanted to reuse most of the settings of the config to create a new (second) PN instance, is there a way I can do it now? probably not, since the original config will be locked (both outside and the inner copy in PN)?

Can you add a method to config that, even with a locked config, lets me clone+modify an existing config? or is it already possible with some Python magic, or similar to the deepcopy function that you're using here

I'd like to do something like (pseudocode):

val config = PNConfiguration(blah, blah, blah)
val pubnub1 = PubNub(config)

val config2 = config.copy(uuid = blah2)
val pubnub2 = PubNub(config2)