Export `ConfigFile` struct which can be de/serialized from and to a configuration file

[sandreae]

📋 Checklist

• [x] Add tests that cover your changes
• [x] Add this PR to the Unreleased section in CHANGELOG.md
• [x] Link this PR to any issues it closes
• [x] New files contain a SPDX license header

[codecov[bot]]

Codecov Report

Attention: 133 lines in your changes are missing coverage. Please review.

Comparison is base (162c350) 92.32% compared to head (8cc9f83) 91.67%.

:exclamation: Current head 8cc9f83 differs from pull request most recent head 59ecbb0. Consider uploading reports for the commit 59ecbb0 to get more accurate results

Files	Patch %	Lines
aquadoggo/src/api/config_file.rs	0.00%	133 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #607 +/- ## ========================================== - Coverage 92.32% 91.67% -0.66% ========================================== Files 109 110 +1 Lines 18681 18839 +158 ========================================== + Hits 17248 17271 +23 - Misses 1433 1568 +135 ```

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