[Fix][scala-sttp][circe] Add Base64OrArrayByteDecoder for format:byte and format:binary JSON properties

[nikhilsu]

Fixes #23618.

cc @clasnake (2017/07), @shijinkui (2018/01), @ramzimaalej (2018/03), @chameleon82 (2020/03), @Bouillie (2020/04) @Fish86 (2023/06)

Adds FlexibleByteArrayDecoder: Decoder[Array[Byte]] to additionalTypeSerializers.mustache for the scala-sttp circe generator.

Problem: Properties with format: byte generate Option[Array[Byte]], but circe's derived Decoder[Array[Byte]] expects a JSON number array. Jackson serializes byte[] fields as Base64 strings, so decoding always fails at runtime with DecodingFailure at .field: Array[Byte]. The existing FileDecoder (used for format: binary JSON properties) is also broken for the same reason, since it delegates to Decoder[Array[Byte]].

Fix: The new decoder tries JSON array first (strict OAS compliance), then falls back to Base64 string decoding

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Summary by cubic

Fixes #23618. Adds Base64OrArrayByteDecoder to the scala-sttp circe generator so format: byte and format: binary fields decode from JSON arrays or Base64 strings without runtime failures.

• Bug Fixes
  • Implemented Base64OrArrayByteDecoder: Decoder[Array[Byte]] (array-first, Base64 fallback).
  • Updated additionalTypeSerializers.mustache with the decoder and java.util.Base64 import.
  • Extended tests and samples to assert decoder emission and map checksum: byte to Option[Array[Byte]].

^{Written for commit caffe64. Summary will update on new commits.}

[nikhilsu]

@wing328 Here is another targeted bug fix which is low risk.

I know 7.22.0 is due today. Can this PR make it or is it too late? :)

Thank you so much for all the reviews so far, btw 🙏

[cubic-dev-ai]

No issues found across 4 files