fix: avro_to_arrow: Handle avro nested nullable struct (union) (apache#7663)

Corrects handling of a nullable struct union.

Signed-off-by: 🐼 Samrose Ahmed 🐼 <[email protected]>

Author: Samrose-Ahmed

datafusion/core/Cargo.toml

@@ -109,6 +109,7 @@ rand_distr = "0.4.3"
 regex = "1.5.4"
 rstest = "0.18.0"
 rust_decimal = { version = "1.27.0", features = ["tokio-pg"] }
+serde_json = "1"
 test-utils = { path = "../../test-utils" }
 thiserror = "1.0.37"
 tokio-postgres = "0.7.7"