Add SKU to Item

[laf-rge]

Fix SKU Field Retrieval and Account Test Issues (Fixes #373)

Changes

This PR addresses two main issues:

1. SKU Field Retrieval Fix

• Fixed issue where SKU field was not being returned in Item.all() queries
• Added test case test_sku_in_all to verify SKU field retrieval
• Removed trailing slashes from API URLs to ensure consistent behavior

2. Account Test Improvements

• Enhanced account test reliability by using shorter, unique identifiers
• Improved test cleanup and isolation
• Fixed test failures related to duplicate account names/numbers

Technical Details

SKU Field Fix

• Modified URL construction in get_single_object to remove trailing slashes
• Added explicit test case to verify SKU field is properly returned in list queries
• Verified SKU field retrieval works in both individual and bulk item queries

Account Test Improvements

• Implemented shorter timestamp format for account identifiers to stay within QB's 20-char limit
• Enhanced test isolation by using unique identifiers for each test run
• Removed unnecessary sleep statements that were masking the real issues

Testing

• All tests are now passing, including:
  • Item tests (including new SKU field test)
  • Account integration tests
  • Unit tests for URL handling
• Verified that SKU field is properly returned in production scenarios
• Confirmed account creation/updates work reliably with new identifier format

Breaking Changes

None. This is a backward-compatible fix that improves existing functionality.

Related Issues

• Fixes issue where SKU field was missing from Item.all() results
• Resolves account test failures due to identifier length and uniqueness

Additional Notes

• The URL trailing slash fix also improves consistency across all API calls
• Account test improvements make the test suite more reliable and faster

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 72.72727% with 9 lines in your changes missing coverage. Please review.

Project coverage is 93.34%. Comparing base (67141c2) to head (67e94c2).

Files with missing lines	Patch %	Lines
quickbooks/mixins.py	41.66%	3 Missing and 4 partials ⚠️
tests/unit/test_client.py	75.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #379      +/-   ##
==========================================
- Coverage   93.53%   93.34%   -0.20%     
==========================================
  Files         104      104              
  Lines        3991     3994       +3     
  Branches      108      105       -3     
==========================================
- Hits         3733     3728       -5     
- Misses        219      221       +2     
- Partials       39       45       +6     

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[laf-rge]

Got annoyed with the broken tests so this fixes that as well. If you want me to break that out I can but it is straightforward. (drops 2.x mock external dependency and mocks the auth_client)