fix: use field-presence checks in union deserializers to prevent misclassification

[fern-api]

2.1.0 → 2.1.1

Previously, all union response deserializers attempted blind convertValue
calls in sequence, catching RuntimeException to fall through to the next
candidate type. This approach could silently misclassify a response payload
as the wrong union variant when Jackson's lenient conversion succeeded on an
incompatible type.

The deserializers now inspect the raw Map keys first, requiring the
presence of discriminating fields before attempting conversion. This makes
variant selection deterministic and prevents incorrect deserialization of
ambiguous payloads.

Key changes:

• GetAggregationCountResponse and PostAggregationCountResponse deserializers now gate on status, total_hits, page, total_pages, and page_size keys before attempting conversion to AggregationCountResponseDto or FailedAggregationCountResponseDto
• GetAuthorsResponse and PostAuthorsResponse deserializers apply the same pagination-field guard before converting to SearchResponseDto or FailedAuthorsResponseDto
• GetLatestHeadlinesResponse, PostLatestHeadlinesResponse, GetSearchResponse, and PostSearchResponse deserializers additionally require clusters_count and clusters keys before attempting ClusteredSearchResponseDto conversion
• AggregationCountResponseDtoAggregations deserializer gates on aggregation_count key before attempting AggregationItem conversion
• SourcesResponseDtoSourcesItem deserializer gates on domain_url key before attempting SourceInfo conversion

🌿 Generated with Fern

[oscatcher]

lgtm