Ppt mode

[KSDaemon]

This PR includes:

• New feature: Payload Passthru Mode (PPT Mode for short). PPT Mode is an evolution of payload_transparency feature and now is officially described in  WAMP spec
• Tests for PPT Mode
• Extended serializers with methods for item serialization (in addition to serialization of the whole wamp message)
• As new attributes were added to options/details parameter, some API method were modified (e.g. instead of passing just one positional boolean argument for progress, now options are done mostly everywhere across library in same manner: named arguments to be able to pass all desired options at once)
• Some parts were refactored
• Tests were refactored a bit
• Some preparations for End-2-end encryption (E2EE for short), that runs on top of ppt mode

There are definitely places to refactor and optimize but the main feature is working.

This is the same as https://github.com/konsultaner/connectanum-dart/pull/52 but inside this repo

[KSDaemon]

Hi @konsultaner How is it going?) You wanted to reorder some parts and add some unit tests and rename some code parts...

[konsultaner]

Hi @konsultaner How is it going?) You wanted to reorder some parts and add some unit tests and rename some code parts...

Sorry, I'm having big trouble with another project for about 2 weeks. As soon as I'm done with it I'll come back to this project. 😩

[KSDaemon]

@konsultaner Okay! Good luck resolving all the issues!