Add Iceberg-style API for defining schemas with field IDs

[murali-db]

Currently, creating schemas with field IDs requires verbose boilerplate:

StructType::new_unchecked([
    create_field_with_id("id", DataType::LONG, false, 1),
    create_field_with_id("name", DataType::STRING, true, 2),
]);

// Helper function needed:
fn create_field_with_id(name: &str, data_type: DataType, nullable: bool, id: i64) -> StructField {
    StructField::new(name, data_type, nullable)
        .add_metadata([
            ("delta.columnMapping.id", MetadataValue::Number(id)),
            ("delta.columnMapping.physicalName", MetadataValue::String(format!("col_{}", id))),
        ])
}

Proposal

Add a builder-style API similar to Iceberg for ergonomic schema construction with field IDs:

  StructType::builder()
      .field("id", DataType::LONG).required().id(1).build()
      .field("name", DataType::STRING).nullable().id(2).build()
      .build()

Or method chaining on StructField:

  StructField::new("id", DataType::LONG, false)
      .with_id(1)
      .with_physical_name("col_1")

This would improve readability and reduce boilerplate when working with column mapping, especially in tests and schema evolution scenarios.

[OussamaSaoudi]

A non-builder style like this would be great:

        Schema schema = new Schema(
                Types.NestedField.required(1, "id", Types.LongType.get()),
                Types.NestedField.required(2, "name", Types.StringType.get()),
                Types.NestedField.optional(3, "age", Types.IntegerType.get()),
                Types.NestedField.required(4, "timestamp", Types.TimestampType.withZone()),
                Types.NestedField.optional(
                        5,
                        "address",
                        Types.StructType.of(
                                Types.NestedField.required(6, "street", Types.StringType.get()),
                                Types.NestedField.optional(7, "city", Types.StringType.get()),
                                Types.NestedField.required(8, "zip_code", Types.IntegerType.get())
                        )
                ),
                Types.NestedField.optional(
                        9,
                        "tags",
                        Types.ListType.ofRequired(10, Types.StringType.get())
                ),
                Types.NestedField.optional(
                        11,
                        "properties",
                        Types.MapType.ofRequired(12, 13, Types.StringType.get(), Types.StringType.get())
                )
        );

[OussamaSaoudi]

We'll need to decide on how to do physical names as well.