Add ST_SRID

[jesspav]

This change adds ST_SRID to retrieve a geometry's CRS' SRID.

This is the first step in #28 . Will implement #29 before adding the integration tests to align the schemas.

Example

> select ST_SRID(ST_SetSrid(ST_GeomFromText('POINT (1 1)'), 'EPSG:4837')) as srid;
┌────────┐
│  srid  │
│ uint32 │
╞════════╡
│   4837 │
└────────┘

[Copilot]

Pull Request Overview

This PR adds the ST_SRID function to retrieve the spatial reference system identifier (SRID) from coordinate reference systems. The implementation extends the CRS trait with a new srid() method and provides a scalar UDF for exposing this functionality.

• Add srid() method to the CoordinateReferenceSystem trait
• Implement ST_SRID scalar function that returns the SRID as a UInt32
• Add comprehensive test coverage for both CRS implementations and the new function

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
rust/sedona-schema/src/crs.rs	Add srid() method to CRS trait and implement for AuthorityCode and ProjJSON types
rust/sedona-functions/src/st_srid.rs	New ST_SRID scalar function implementation with comprehensive tests
rust/sedona-functions/src/register.rs	Register the new ST_SRID function in the default function set
rust/sedona-functions/src/lib.rs	Add module declaration for st_srid

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[paleolimbot]

Thank you!