Data API with lexical/analyzer off does not accept explicit "enabled: false" setting for collections

[sl-at-ibm]

(Originally reported by @clun )

Summary:

It should be possible to indicate re-ranking is disabled regardless of whether it'd be possible to enable, but currently the server errors on doing that.

(Tatu: I am guessing option validation done in wrong place [...]).

Description

When the Data API is started without lexical/analyzer support, as is currently the case e.g. for Mission Control, attempts to create a collection with these settings explicitly set to 'disabled' result in an error:

{
  "createCollection": {
    "name": "collection_vector",
    "options": {
      "vector": {
        "dimension": 14,
        "metric": "cosine"
      },
      "lexical": {
        "enabled": false
      },
      "rerank": {
        "enabled": false
      }
    }
  }
}

A payload like the above results in:

{
  "errors": [
    {
      "message": "Reranking feature is not enabled",
      "errorCode": "RERANKING_FEATURE_NOT_ENABLED",
      "family": "REQUEST",
      "scope": "RERANKING",
      "title": "Reranking feature is not enabled",
      "id": "4ff098df-ac53-4c8f-9566-f69ea6bfef18"
    }
  ]
}

Expected behaviour

Since the payload specifies enabled: false (which matches the available support), the expectation is that this collection is created correctly.