Incomplete `gen_ai` nested fields

[AlexRuiz7]

Description

The gen_ai object contains some nested fields which are incomplete.

Valid nested field:

  "sections": {
    "properties": {
      "entropy": {
        "type": "long"
      },
      "name": {
        "ignore_above": 1024,
        "type": "keyword"
      },
      "physical_size": {
        "type": "long"
      },
      "var_entropy": {
        "type": "long"
      },
      "virtual_size": {
        "type": "long"
      }
    },
    "type": "nested"
  }

Invalid nested fields under gen_ai:

  "encoding_formats": {
    "type": "nested"
  },

As you can see, the nested field has no fields actually (properties).

The dangling fields are:

• encoding_formats
• stop_sequences
• finish_reasons

OpenTelemetry documents these fields as a list of strings, so I think that's what these fields should be.