Implements h3ToGeoBoundary function by Ivan Veselov

Why it matters

This feature allows users to convert H3 hexagon indexes into their corresponding geographic polygon boundaries, facilitating spatial analysis and visualization of geospatial data stored in the H3 format within ClickHouse.

How to use it

Use the h3ToGeoBoundary function in your queries by passing an H3 index as input to retrieve the geographic boundary polygon. For example:

SELECT h3ToGeoBoundary(h3_index) FROM table_name;