Detach add_document and add_schema from TestDatabase

[cafca]

Refactors these methods as independent helpers as discussed in #141 (comment)

📋 Checklist

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

[codecov]

Codecov Report

Merging #237 (477a403) into development (c95a789) will decrease coverage by 0.16%.
The diff coverage is 100.00%.

❗ Current head 477a403 differs from pull request most recent head c335e53. Consider uploading reports for the commit c335e53 to get more accurate results

@@               Coverage Diff               @@
##           development     #237      +/-   ##
===============================================
- Coverage        94.00%   93.83%   -0.17%     
===============================================
  Files               59       58       -1     
  Lines             4917     4805     -112     
===============================================
- Hits              4622     4509     -113     
- Misses             295      296       +1     

Impacted Files	Coverage Δ
aquadoggo/src/db/stores/test_utils/store.rs	92.15% <ø> (-7.85%)	⬇️
aquadoggo/src/db/stores/test_utils/helpers.rs	96.34% <100.00%> (-3.66%)	⬇️
aquadoggo/src/graphql/client/dynamic_query.rs	91.82% <100.00%> (+0.55%)	⬆️
...quadoggo/src/graphql/client/dynamic_types/tests.rs	100.00% <100.00%> (ø)
aquadoggo/src/graphql/client/tests.rs	100.00% <100.00%> (ø)
aquadoggo/src/graphql/client/utils.rs	92.59% <100.00%> (ø)
aquadoggo/src/graphql/schema.rs	92.64% <100.00%> (ø)
aquadoggo/src/node.rs	0.00% <0.00%> (-84.62%)	⬇️
.../src/graphql/client/dynamic_types/document_meta.rs	62.50% <0.00%> (-18.46%)	⬇️
aquadoggo/src/graphql/scalars/seq_num_scalar.rs	88.88% <0.00%> (-8.62%)	⬇️
... and 34 more

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