Add definedBy validation

[AFOliveira]

As mentioned in #319. Please let me know if how I structured it makes sense. I put it under the arch test since I believe it kind of belongs to it, but it maybe could be done separately

[dhower-qc]

This is something that should be handled by JSON Schema, but it's not...

If you follow the schema, eventually you see that the string should match an "extension_name":

    "extension_name": {
      "type": "string",
      "pattern": "^([A-WY])|([SXZ][a-z0-9]+)$"
    },

The pattern is supposed to exclude a comma. But it's actually accepting any string; see https://stackoverflow.com/a/51959769. The whole thing needs to be wrapped in parens:

      "pattern": "^(([A-WY])|([SXZ][a-z0-9]+))$"

With that change, I think it solves the problem.

[AFOliveira]

@dhower-qc Alright! And you've done that in #350, right? If so, I'll just close this

[dhower-qc]

Actually, I haven't. I fixed the source files, but didn't notice the bug in the schema until now.

[dhower-qc]

I just added it to #350, so we can close this now. Thanks!