Set cert location based on where they actually are in the filesystem

[nicklan]

This works, but will search the FS on every request.

Looking for guidance on the idiomatic way in a DuckDB extension to store this between calls.

[samansmink]

In the Azure extension we use the ClientContext::registered_state for this, see here

This is likely the cleanest way to solve this, but perhaps a little overkill for the prototyping state of the extension and might lead to double work if we end up refactoring.

Alternatively perhaps for now its fine to search the FS on every request or perhaps doing it once on extension load storing the resulting path in a global variable. Note that because the extension initialization function is guaranteed to be the first thing that is called and will never be called again, this is safe to do without locking.