increase code coverage for estimate item category / estimate message …

[becoded]

…/ expense category

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.72%. Comparing base (00a3f1c) to head (da16017).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #102      +/-   ##
==========================================
+ Coverage   69.97%   71.72%   +1.75%     
==========================================
  Files          24       24              
  Lines        1542     1542              
==========================================
+ Hits         1079     1106      +27     
+ Misses        337      315      -22     
+ Partials      126      121       -5     

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[Copilot]

Pull Request Overview

This PR increases test coverage for three harvest API components by adding error case tests and string method tests. The changes focus on improving test coverage for estimate item categories, estimate messages, and expense categories.

Key changes:

• Added error case tests for API operations that previously only tested successful scenarios
• Added comprehensive string method tests for data structures and their list types
• Enhanced existing error handling test assertions to verify nil return values

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
harvest/expense_category_test.go	Added error case tests for Create/Update operations and comprehensive String method tests for ExpenseCategory and ExpenseCategoryList
harvest/estimate_message_test.go	Added error case tests for estimate status change operations and String method tests for EstimateMessage and EstimateMessageList
harvest/estimate_item_category_test.go	Added error case tests for Create/Update operations and String method tests for EstimateItemCategory and EstimateItemCategoryList

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