Allow to pass custom spec -> definition for API entity

[HolmesInc]

Describe Request:

I would like to pass custom definitions (like Kafka topics) to a catalog-info API entity definition but because of hardcoded validator rule it's impossible to do that and pass validation.
Could you please add the possibility to pass definition options?

Examples:

apiVersion: backstage.io/v1alpha1
kind: API
metadata:
  namespace: my-namespace
  name: api-name
  annotations:
    gitlab.com/project-id: '12345678'
spec:
  type: api-type
  owner: group:owner-group
  lifecycle: experimental
  definition:
    $topic: topic.area.name.1

Validation of this catalog info will fail because of hardcoded tule here:

function modifyPlaceholders(obj) {
  for (const k in obj) {
    if (typeof obj[k] === 'object') {
      try {
        if (obj[k].$text || obj[k].$openapi || obj[k].$asyncapi) {
          obj[k] = 'DUMMY TEXT';
          return;
        }
      } catch (e) {
        throw new Error(
          `Placeholder with name '${k}' is empty. Please remove it or populate it.`,
        );
      }
      modifyPlaceholders(obj[k]);
    }
  }
}

But with the following update, it'll pass:

function modifyPlaceholders(obj, condition) {
  for (const k in obj) {
    if (typeof obj[k] === 'object') {
      try {
        for (const c of condition) {
          if (obj[k][c]) {
            obj[k] = 'DUMMY TEXT';
            return;
          }
        }
      } catch (e) {
        throw new Error(
          `Placeholder with name '${k}' is empty. Please remove it or populate it.`,
        );
      }
      modifyPlaceholders(obj[k], condition);
    }
  }
}

Where const condition = ['$text', '$openapi', '$asyncapi', '$topic']

Supporting Documentation Links:

https://github.com/RoadieHQ/roadie-backstage-plugins/blob/0b7f60228b6de7c7d0baa5033aff6b105d258d5b/utils/roadie-backstage-entity-validator/src/validator.js#L39C1-L55C2

[Xantier]

Thanks! Yeah, that sounds like a good idea. Looking forward to the PR