Support property condition: `simple`

[barmac]

"condition": {
  "examples": [
    {
      "type": "simple",
      "property": "httpMethod",
      "equals": "GET"
    },
    {
      "type": "simple",
      "property": "httpMethod",
      "oneOf": [ "POST", "PUT", "DELETE" ]
    }
  ]
}

Closes #54

[barmac]

Note for reviewers: This PR is targeted at next. This is the branch from which we will release an alpha version of the schema. If we need to do any breaking changes, we will do it on next. When condition schema is settled, we will merge to master.

[nikku]

Should we not adopt develop and master/main? We have it in some parts of our tooling, and it works.

[barmac]

We could do that, sure.

[barmac]

next -> develop is done

[barmac]

Thanks for the review. I will add code change you suggested and the test cases.

[barmac]

Ready for second round.