fix: make sure headers must be object type

[derberg]

Description

• According to specification message headers must be defined as a schema of an object. Other types are not allowed.
• Solution based on https://json-schema.org/understanding-json-schema/reference/combining.html#id5

now validation fails with:

"headers": {
    "type": "integer",
    "enum": [1, 2]
}

but it is allowing:

"headers": {
    "type": "object",
    "properties": {
      "my-app-header": {
        "type": "integer",
        "minimum": 0,
        "maximum": 100
      }
    }
  }

Related issue(s)
See also asyncapi/parser-js#68

Comment
I assume that once this is merged, I also need to create a PR to asyncapi-node. See also #395

[fmvilas]

Looks good to me. Just left a suggestion.

[derberg]

@fmvilas good point, const is better, have a look now

[asyncapi-bot]

🎉 This PR is included in version 1.0.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[derberg]

It is actually not included in the release. This was an unintentional release caused by the release automation initial run. 1.0 version of the spec was released a long time ago. The release mentioned by the bot was removed.

[asyncapi-bot]

🎉 This PR is included in version 2.1.0-2021-06-release.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[asyncapi-bot]

🎉 This PR is included in version 2.1.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀