Binary union packet definition support

[git-gawwyt]

Reason\Context

Some highly constrained devices/transport protocols find the overheads of JSON or even protobuf to be too large to handle. Such as when using Lora or CAN for transport or running a sensor attached to a micro (e.g. an ATMEGA324PB).

In these situations, event payloads are encoded into space-optimized binary unions (see below for C++ example). It would be nice if the same tooling for defining the event systems further upstream could be used at this level so the solution can be approached as a whole.

C++ union example for clarity

typedef struct {
	//single byte used to identify packet for deserilizer
	unsigned short messageType: 8;
	//two one bit boolean prop's and a six bit number packed into another byte
	unsigned short booleanPropOne: 1;
	unsigned short booleanPropTwo: 1;
	unsigned short sixBitIntergerProp: 6;
} AyncStructExample;

The above struct is a simplified example but the general idea is to pack as much useful information into what might be a very limited transport payload size (8 bytes in CAN)

Implementation ideas
To keep impact outside of this niche use case limited, it might be a good idea to implement this as an extension of the binary format for a string.

ie:

type: object
discriminator: messageType
required:
- body
properties:
  body:
    type: string

    format: binary
    fields:
      messageType:
        type: interger
        bits: 8
      booleanPropOne:
        type: boolean
        bits: 1
      booleanPropTwo:
        type: boolean
        bits: 1
      sixBitIntProp:
        type: integer
        bits: 6

an alternative would be to extend integer to have an optional bits field and create a new union format for objects that indicates it should be de/serialized as such.

ie:

type: object
discriminator: messageType
format: union
required:
- messageType
properties:
    messageType:
      type: interger
      bits: 8
    booleanPropOne:
      type: boolean
      bits: 1
    booleanPropTwo:
      type: boolean
      bits: 1
    sixBitIntProp:
      type: integer
      bits: 6

Took a step back from "just doing it" to check which implementation approach the maintainers would go with and get some feedback.