arrow-flight CommandGetDbSchemas schema not matching documentation

[jwimberl]

Describe the bug
Going back some time (< release 33.0.0) the documentation for CommandGetDbSchemas states the catalog_name field should be nullable:

The returned Arrow schema will be: < catalog_name: utf8, db_schema_name: utf8 not null

https://docs.rs/arrow-flight/55.0.0/arrow_flight/sql/struct.CommandGetDbSchemas.html

However, using arrow-flight v53.2.0 (the newest version I'm able to test with easily), the returned schema has a non-nullable catalog_name field.

To Reproduce
Given a CommandGetDbSchemas object cmd, examine

dbg!(&cmd.into_builder().schema()

Output:

[... my file...] &cmd.into_builder().schema() = Schema {
    fields: [
        Field {
            name: "catalog_name",
            data_type: Utf8,
            nullable: false,
            dict_id: 0,
            dict_is_ordered: false,
            metadata: {},
        },
        Field {
            name: "db_schema_name",
            data_type: Utf8,
            nullable: false,
            dict_id: 0,
            dict_is_ordered: false,
            metadata: {},
        },
    ],
    metadata: {},
}

Expected behavior
nullable should be true in the catalog_name field to match the documentation. This is also the downstream expectation, e.g. in adbc_driver_manager.adbc_get_objects() when using adbc_driver_flightsql.

Additional context
I’m using arrow-flight v53.2.0 -- ideally I’d test this on the newest arrow-flight version, but that would be a time investment for compatibility reasons, and I don’t see mention of CommandDbGetTables in release notes or issues. If there is a good chance that this was fixed in a subsequent release, I can make the effort to update and retest.

[xborder]

I believe this was fixed by #7637