Add interface definition + stubs for serializer
Add implementation for ws_serializer_json_serializer_new()
Add implementation for serialize() callback
Add keys for event serialization
Add interface + stubs + states for serializer state helper(s)
Add implementation for serializer_context_new()
Add helper for generating a new key in the buffer
Add implementation for serialize_event()
Add test file for serializer test
Add test for serializing a ws_message (which is not valid)
Add test for serializing an event
Add test for too small buffer
Minify serialize_event()

We actually do not need any states, so rip them out.

We serialize into an own buffer, so we don't need to store a state here.
Fixup for serialize()
Removed unused states
Add support for object-id serializing
Add test for event with ctx: obj-id serialization