Re-write src

[znichollscr]

Description

Checklist

Please confirm that this pull request has done the following:

• [x] Tests added
• [x] Documentation added (where applicable)
• [x] Changelog item added to changelog/

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 82.88191% with 158 lines in your changes missing coverage. Please review.

Project coverage is 82.82%. Comparing base (d9d7200) to head (a088690). Report is 33 commits behind head on main.

Files	Patch %	Lines
src/input4mips_validation/cvs/drs.py	78.15%	27 Missing and 18 partials :warning:
src/input4mips_validation/dataset/dataset.py	75.00%	17 Missing and 14 partials :warning:
src/input4mips_validation/validation/__init__.py	68.65%	18 Missing and 3 partials :warning:
src/input4mips_validation/cli/__init__.py	78.12%	8 Missing and 6 partials :warning:
src/input4mips_validation/database/database.py	80.39%	7 Missing and 3 partials :warning:
src/input4mips_validation/serialisation.py	58.33%	8 Missing and 2 partials :warning:
src/input4mips_validation/cvs/license.py	84.74%	8 Missing and 1 partial :warning:
src/input4mips_validation/validation/cf_checker.py	64.70%	5 Missing and 1 partial :warning:
src/input4mips_validation/inference/from_data.py	78.94%	3 Missing and 1 partial :warning:
src/input4mips_validation/xarray_helpers/time.py	75.00%	2 Missing and 1 partial :warning:
... and 3 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #31 +/- ## ========================================== - Coverage 85.73% 82.82% -2.92% ========================================== Files 22 30 +8 Lines 694 1170 +476 Branches 80 175 +95 ========================================== + Hits 595 969 +374 - Misses 82 143 +61 - Partials 17 58 +41 ```

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