[Feature] Global Defaults

[josepsolerpla]

There is no way to create a custom validator for all types, like "max: 3" on "number" type.

We can create default custom for individual types but is not very efficient.

defaults: { 
	"object": {
		custom(value, errors, schema) { doSomething() }
		return value;
	},
	"object": {
		custom(value, errors, schema) { doSomething() }
		return value;
	}
}

Adding a "globalDefault" on the config and adding on the 'lib > validator.js > class Validator > getRuleFromSchema > when "const rule"' is created adding the global default one.

const rule = {
	messages: Object.assign({}, this.messages, schema.messages),
	schema: deepExtend(schema, this.defaults[schema.type], this.globalDefault, { skipIfExist: true }),
	ruleFunction: ruleFunction,
};

Even doing something like an expression will be great.

defaults: { 
		"*": {
			custom(value, errors, schema) { doSomething() }
			return value;
		}
	}
}

In my case i would like to add a auth rule on moleculer params, something like this.

id: { type: "string", auth: true }

And this will be translated on rule string to:

if (schema.auth === true) {
	src.push(`
		if (isValidateToken(token) === false) {
			${this.makeError({ type: "authError", expected: "Token must to be valid", actual: "origValue", messages })}
		}
	`);
}

Moleculer.js problem: i manage to do this using middlewares but param validation is validated before middleware execute