Allow indexed_shape-only geo_shape and xy_shape queries

[Tejashribambal19]

Summary

Fixes #1160.

The current API specification marks shape as required in both GeoShapeQueryField and XyShapeQueryField. However, OpenSearch supports pre-indexed shape queries using indexed_shape without an accompanying shape, as documented.

Because this specification is the source of truth for generated clients, the current requirement prevents clients from constructing valid indexed_shape-only queries.

This PR removes the shape requirement from both schemas, allowing both inline shape queries and pre-indexed indexed_shape queries.

Changes

• Remove required: [shape] from GeoShapeQueryField
• Remove required: [shape] from XyShapeQueryField

Motivation

The OpenSearch documentation describes shape and indexed_shape as alternative ways to define a geo/xy shape query. Requiring shape makes valid pre-indexed shape queries fail schema validation and propagates incorrect constraints to generated clients.

This change aligns the API specification with the documented query behavior.

Testing

• Verified that the schema changes are limited to GeoShapeQueryField and XyShapeQueryField.
• Existing query behavior remains unchanged for inline shape queries.

Notes

The current specification tests cover inline shape queries but do not include coverage for the indexed_shape path. This PR focuses on correcting the schema; regression tests for indexed_shape can be added separately if maintainers prefer additional coverage.

[lsh1215]

Thanks for picking this up, @Tejashribambal19 — I opened the linked issue #1160. This unblocks the immediate case; I left two inline notes suggesting we model exactly one of shape/indexed_shape (via the existing TermsLookup oneOf pattern) instead of dropping required, since the contract is "one or the other, not both."

One more gap: there's no test coverage for the indexed_shape path yet — the existing geo_shape_* / xy_shape_* stories only exercise inline shape (open question #4 in the issue). I have a branch with the oneOf modeling plus geo_shape_indexed_shape / xy_shape_indexed_shape stories, validated against the merged schema (lint:spec / merge / unit all green). Happy to fold those into this PR or open an alternative — whichever you and the maintainers prefer.

[lsh1215]

Dropping required unblocks indexed_shape-only, but it also makes both shape+indexed_shape and neither valid. Per the docs and @xluo-aws (opensearch-java#2011), it should be exactly one — already modeled in this same file by TermsLookup:

allOf:
  - oneOf:
      - type: object
        properties:
          indexed_shape: { $ref: '#/components/schemas/FieldLookup' }
        required: [indexed_shape]
      - type: object
        properties:
          shape: { $ref: '#/components/schemas/GeoShape' }
        required: [shape]

[lsh1215]

Same here — XyShapeQueryField needs the same exactly-one allOf/oneOf treatment (with XyShape instead of GeoShape).