Add missing ChangeType enum and doc in C++. Add test coverage for ChangeType in integration test.

[leekeiabstraction]

Purpose

Linked issue: close #333

Brief change log

• Add missing ChangeType enum in C++.
• Add missing ChangeType enum documentation for C++.
• Add test coverage for ChangeType in integration test.

[leekeiabstraction]

@fresh-borzoni Appreciate a review here 🙏

[fresh-borzoni]

@leekeiabstraction

it's already added in #330
I haven't added docs though, so let's wait until it gets merged, it's easier to resolve conflicts here, since it's smaller

[leekeiabstraction]

Converted to draft, will push the doc part after #330 gets merged

[leekeiabstraction]

Updated PR to include API doc changes after #330 has been merged. PTAL!

[fresh-borzoni]

@leekeiabstraction Ty, LGTM 👍
Would you mind to add short desc as well? You had it in your PR, it was good addition

inline const char* ChangeTypeShortString(ChangeType ct) {
    switch (ct) {
        case ChangeType::AppendOnly: return "+A";
        case ChangeType::Insert: return "+I";
        case ChangeType::UpdateBefore: return "-U";
        case ChangeType::UpdateAfter: return "+U";
        case ChangeType::Delete: return "-D";
    }
    return "??";
}

[leekeiabstraction]

Thank you Anton! Updated.