Make meta as a third parameter in actions, guards, services

[cybervaldez]

Can we have meta as a standard third parameter for actions, guards, services? Metas are a great way to describe a node especially since compared to context they are read only, it also works like a bridge for machine logic and UI. For ex:

type: 'parallel',
states : {
  age: {
    meta : { input_type: 'number' },
    initial : 'idle',
    states : { idle: {}, active : {} }
  },
  name : {
    meta: { input_type: 'group', require: ['first_name', 'last_name'] },
    initial : 'idle',
    states : { idle: {}, active : {} }
  }
},
on : {
  VALIDATE : 'validate',
  ASSIGN: 'assignValue'
}
},{
actions : {
  validate: (context, event, meta){
    if(meta.input_type === 'number'){
      // ...
    } else if(meta.input_type === 'group') {
      // ...
    } 
  },
  assignValue : assign((context,event,meta)=>{
    if(meta.input_type === 'number'){
        value = ... // parse with yup/zod,
    }

    return {
       [event.key]: value 
    }
  })
}

We can now share the same logic with the UI.
<input type={current.meta.age.input_type} onChange={(e)=>send({ type: 'ASSIGN', key : 'age', value : e.target.value }) } />

On top of this, exposing meta on the visualizer would make the machine more readable.

Caveats/Issues:

1. With how meta is currently laid out requires the knowledge of the state node ids which isn't what we want for actions, services, guards but aggregating meta like in the docs would solve this.

2. The third parameter in guards is reserved for custom guards.