test(avro-to-json): add unit tests for `avro_init` configuration parsing

[WilliamBerryiii]

Description

Follow-up from PR #357 review comment by @auyidi1.

All 7 wireFormat tests added in #357 call parse_with_schema_inner directly. There is no unit test coverage for the avro_init configuration parsing logic itself.

Missing Test Coverage

The following scenarios need unit tests:

• Case-insensitive matching — e.g., "CONFLUENT", "Confluent", " raw " (trim + lowercase)
• Unknown value defaulting — e.g., "invalid" → Auto with warning
• Missing wireFormat — defaults to Auto
• OnceLock::set behavior — the let _ = WIRE_FORMAT.set(...) silently ignores errors if called twice

Location

src/500-application/512-avro-to-json/operators/avro-to-json/src/lib.rs

Context

PR #357 introduced the WireFormat enum and avro_init configuration parsing with trim().to_lowercase() transformations. While integration testing may catch some of these, dedicated unit tests for the config parsing logic would be valuable given the string transformations involved.

Related

• PR: feat(avro-to-json): add wireFormat configuration parameter #357
• Original feature issue: feat(avro-to-json): add wireFormat configuration parameter for deterministic Avro parsing #337