handle nested struct in schemaString (#257)

Handle parsing nested structs in `schemaString`. Setting iceberg compat
causes this. Also enable the iceberg_compat_v1 test for dat, since we do
now support column mapping.

Closes #253 .

acceptance/src/data.rs

@@ -62,9 +62,7 @@ pub fn sort_record_batch(batch: RecordBatch) -> DeltaResult<RecordBatch> {
     Ok(RecordBatch::try_new(batch.schema(), columns)?)
 }
 
-static SKIPPED_TESTS: &[&str; 2] = &[
-    // iceberg compat requires column mapping
-    "iceberg_compat_v1",
+static SKIPPED_TESTS: &[&str; 1] = &[
     // For multi_partitioned_2: The golden table stores the timestamp as an INT96 (which is
     // nanosecond precision), while the spec says we should read partition columns as
     // microseconds. This means the read and golden data don't line up. When this is released in

kernel/src/schema.rs

@@ -21,6 +21,11 @@ pub enum MetadataValue {
     Number(i32),
     String(String),
     Boolean(bool),
+    // The [PROTOCOL](https://github.com/delta-io/delta/blob/master/PROTOCOL.md#struct-field) states
+    // only that the metadata is "A JSON map containing information about this column.", so we can
+    // actually have any valid json here. `Other` is therefore a catchall for things we don't need
+    // to handle.
+    Other(serde_json::Value),
 }
 
 impl From<String> for MetadataValue {