[BUG] `shape` should not be required in `GeoShapeQueryField` (blocks pre-indexed shape queries in generated clients)

[lsh1215]

What is the bug?

The GeoShapeQueryField schema marks shape as required, but the OpenSearch geo_shape query supports a pre-indexed shape form that uses indexed_shape and no sibling shape. Because this spec is the source of truth for generated clients, the requiredness propagates downstream and makes it impossible to build a pre-indexed shape query with the generated classes.

Current schema (spec/schemas/_common.query_dsl.yaml, main):

GeoShapeQueryField:
  type: object
  properties:
    indexed_shape:
      $ref: '#/components/schemas/FieldLookup'
    shape:
      $ref: '#/components/schemas/GeoShape'
    relation:
      $ref: '_common.yaml#/components/schemas/GeoShapeRelation'
  required:
    - shape

Per the docs, shape and indexed_shape are alternatives (one or the other, not both):
https://docs.opensearch.org/latest/query-dsl/geo-and-xy/geoshape/#using-a-pre-indexed-shape-definition

How can one reproduce the bug?

A pre-indexed shape query is valid against OpenSearch. This is the pre-indexed example from the docs (index pre-indexed-shapes, document id search_triangle, path boundaries):

GET /testindex/_search
{
  "query": {
    "geo_shape": {
      "location": {
        "indexed_shape": {
          "index": "pre-indexed-shapes",
          "id": "search_triangle",
          "path": "boundaries"
        },
        "relation": "WITHIN"
      }
    }
  }
}

Validating this body against the current schema fails because shape is missing, even though the query has no inline shape by design.

How did this happen? (timeline)

• PR Update spec and add tests for xy, geo shape, and geo bounding box query #531 introduced the geo shape field schema (then named GeoShapeField) with required: - shape. At that time the schema had only shape and relation, with no indexed_shape, so requiring shape was consistent.
• indexed_shape was added to the schema later, but required: - shape was not revisited. That produced the current mismatch: indexed_shape is optional while shape stays mandatory.

(Origin PR: #531)

Downstream impact

Reported in the Java client: opensearch-project/opensearch-java#2011

Maintainer confirmation on that issue (xluo-aws):

• either shape or indexed_shape can be used, but not both;
• the fix should be made in the API spec first, otherwise the change in the client repo is overwritten by regeneration.

Generated client repro (opensearch-java):

new Query.Builder()
    .geoShape(new GeoShapeQuery.Builder()
        .field("some")
        .shape(shape -> shape.indexedShape(i -> i.index("some").id("id").path("path")))
        .build())
    .build();
// GeoShapeQueryField requires `shape`, so an indexed_shape-only query can't be built.

What is the expected behavior?

The schema should allow a GeoShapeQueryField that provides indexed_shape without shape, matching the documented pre-indexed shape query.

Open questions for maintainers (how to model the contract)

I'd like to align on the intended schema shape before opening a PR:

1. Is the contract "exactly one of shape / indexed_shape" (mutually exclusive), or "at least one of them"? The docs read as one-or-the-other.
2. How should this be expressed in the spec: simply dropping required: - shape, or using oneOf / minProperties / another construct that the codegen and existing spec conventions support?
3. XyShapeQueryField has the same issue. It carries an identical required: - shape alongside an optional indexed_shape, so it likely needs the same treatment (it was introduced as XyShapeField in Update spec and add tests for xy, geo shape, and geo bounding box query #531 and later renamed, same as the geo variant).
4. Which spec tests should be updated or added? There are existing tests under tests/default/_core/search/query/geo_shape_*.yaml from Update spec and add tests for xy, geo shape, and geo bounding box query #531, but none cover the indexed_shape path.

Additional context

• Docs source: https://github.com/opensearch-project/documentation-website/blob/main/_query-dsl/geo-and-xy/geoshape.md
• Current schema: https://github.com/opensearch-project/opensearch-api-specification/blob/main/spec/schemas/_common.query_dsl.yaml