ENH: Test datatypes and values in Extern C interface

Integration tests for https://gitlab.indiscale.com/caosdb/customers/lfpb/management/-/issues/420 and caosdb-cpplib!13 (merged)

Almost solely whitespace changes that my clang-tidy performed, the only real changes concern the way strings are "returned" by the Extern C interface.

added 5 commits

• 7bd64f95...8da9fbf6 - 5 commits from branch f-consolidation

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added 2 commits

• 7f5ab863 - ENH: Use correct string getters
• f638ff39 - STY: autoformatted

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mentioned in merge request caosdb-cpplib!13 (merged)

added 3 commits

• f638ff39...8f310e43 - 2 commits from branch f-consolidation
• bf337c11 - Merge branch 'f-consolidation' into f-consolidate-c

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deleted the f-consolidation branch. This merge request now targets the dev branch

added 3 commits

• 00a5409c - 1 commit from branch dev
• 7df6f3f3 - STY: WS
• dc449fda - Merge branch 'dev' into f-consolidate-c

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requested review from @henrik

changed the description

resolved all threads

mentioned in commit 4bfad1ea

merged