add system settings resource

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.69027% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 85.38%. Comparing base (b7766e1) to head (656addb). Report is 2 commits behind head on main.

Files	Patch %	Lines
internal/provider/resource_system_settings.go	94.54%	3 Missing and 3 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #502 +/- ## ========================================== + Coverage 85.28% 85.38% +0.10% ========================================== Files 81 82 +1 Lines 7928 8040 +112 ========================================== + Hits 6761 6865 +104 - Misses 765 769 +4 - Partials 402 406 +4 ```

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