fix: throw error instead of assertion for CA config read failure

[pfitzseb]

Makes the error reporting for that code path a bit more obvious. In light of #54, we could also mention the env vars here?

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 74.68%. Comparing base (10f7b7b) to head (3e02148).
⚠️ Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ssl.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #55      +/-   ##
==========================================
- Coverage   77.56%   74.68%   -2.88%     
==========================================
  Files           2        2              
  Lines        1083     1114      +31     
==========================================
- Hits          840      832       -8     
- Misses        243      282      +39     

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[aviks]

We should incorporate this for help debugging future errors, but a proper fix for #54 also needs to be made.