🧪 [testing improvement] Add tests for TusServletRequest

[tomdesair]

🎯 What: The testing gap addressed: Missing test file for TusServletRequest. Created TusServletRequestTest and MockServletInputStream.
📊 Coverage: What scenarios are now tested: standard and chunked input streams, input streams with checksum calculations (both standard and chunked), processor registration, and header fallbacks.
✨ Result: The improvement in test coverage: The new tests successfully cover 100% of the modified lines (which were none since it was an addition) and significantly increases test coverage of the TusServletRequest class.

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PR created automatically by Jules for task 3677208701501500505 started by @tomdesair

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[coveralls]

coverage: 94.667% (+0.03%) from 94.642% — feature/tus-servlet-request-tests-3677208701501500505 into master