feat(rust/sedona-function): Implement ST_AsEWKB with item CRS support

[paleolimbot]

This PR implements an EWKB writer and uses it to implement ST_AsEWKB.

import sedona.db

sd = sedona.db.connect()

sd.sql("SELECT ST_AsEWKB(ST_GeomFromEWKT('SRID=26920;POINT (0 1)')) as ewkb").show()
#> ┌────────────────────────────────────────────────────┐
#> │                        ewkb                        │
#> │                       binary                       │
#> ╞════════════════════════════════════════════════════╡
#> │ 0101000020286900000000000000000000000000000000f03f │
#> └────────────────────────────────────────────────────┘

# Regular binary is shorter because it doesn't have the embedded SRID
sd.sql("SELECT ST_AsBinary(ST_GeomFromEWKT('SRID=26920;POINT (0 1)')) as ewkb").show()
#> ┌────────────────────────────────────────────┐
#> │                    ewkb                    │
#> │                   binary                   │
#> ╞════════════════════════════════════════════╡
#> │ 01010000000000000000000000000000000000f03f │
#> └────────────────────────────────────────────┘

[Copilot]

Pull request overview

This PR implements the ST_AsEWKB function with support for CRS (Coordinate Reference System) metadata, enabling EWKB (Extended Well-Known Binary) output that includes SRID information.

Changes:

• Adds EWKB writer implementation with SRID support for all geometry types
• Implements ST_AsEWKB scalar UDF with both type-level and item-level CRS support
• Adds comprehensive test coverage for EWKB serialization across geometry types and dimensions

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
rust/sedona-geometry/src/lib.rs	Exports new ewkb_factory module
rust/sedona-geometry/src/ewkb_factory.rs	Implements EWKB writer with SRID encoding for all geometry types
rust/sedona-functions/src/st_asewkb.rs	Implements ST_AsEWKB UDF with CRS support
rust/sedona-functions/src/register.rs	Registers ST_AsEWKB function in default function set
rust/sedona-functions/src/lib.rs	Declares st_asewkb module
rust/sedona-functions/src/executor.rs	Adds support for iterating over item CRS struct types
python/sedonadb/tests/functions/test_wkb.py	Adds parametrized tests comparing SedonaDB and PostGIS EWKB output
python/sedonadb/python/sedonadb/testing.py	Extends geom_or_null helper to support SRID parameter
python/sedonadb/pyproject.toml	Adds pandas version constraint as workaround

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