Fix empty LocalizedText binary field encoding

[cristipogacean]

Description

Omit empty Locale and Text fields from the OPC UA Binary DataEncoding for LocalizedText, as required by OPC 10000-6, Section 5.2.2.14, Table 24. Add wire-format tests for empty and non-empty fields, including translation-backed localized text.

Validation:

• git diff --check passed before commit.
• dotnet build tests\Opc.Ua.Types.Tests\Opc.Ua.Types.Tests.csproj --framework net10.0 --no-restore --verbosity minimal -p:NuGetAudit=false could not complete because access to https://api.nuget.org/v3/index.json failed with NU1301 and a TLS handshake error.

Related Issues

No related issue.

Checklist

• I have signed the CLA and read the CONTRIBUTING doc.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added all necessary documentation.
• I have verified that my changes do not introduce (new) build or analyzer warnings.
• I ran all tests locally using the UA.slnx solution against at least .net framework and .net 10, and all passed.
• I fixed all failing and flaky tests in the CI pipelines and all CodeQL warnings.
• I have addressed all PR feedback received.

[Copilot]

🟡 Changes recommended

Three nullable buffer assignments trigger warnings in the warnings-as-errors build.

1 open finding

• Nullable buffer assignment fails warnings-as-errors build · New

What changed in this PR

Updates binary encoding to omit empty LocalizedText locale/text fields per OPC UA requirements.

Changes:

• Uses encoding-mask bits only for non-empty fields.
• Adds wire-format and round-trip tests.

File	Description
src/​Opc.Ua.Types/​Encoders/​BinaryEncoder.cs	Omits empty localized-text fields.
tests/​Opc.Ua.Types.Tests/​BuiltIn/​LocalizedTextTests.cs	Adds binary encoding tests.

🧠 Review effort: Balanced

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[github-actions]

Code coverage

✅ Coverage gate passed.

Check	Result	Threshold
✅ Project line rate	88.61% (306553/345957 lines)	>= 70.00%
✅ Project branch rate	79.06%	>= 60.00%
✅ Patch coverage	100.00% (11/11 changed lines)	>= 60.00% (<= 100 changed lines, advisory)
ℹ️ Baseline delta (advisory)	+15.01 pp	73.60% recorded

Coverage is above the recorded baseline - consider ratcheting coverage-thresholds.json.

_{Thresholds live in coverage-thresholds.json. Whole report before exclusions: line 87.74%, branch 78.26%.}

[marcschier]

Need to fix the build errors on AOT

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.84%. Comparing base (2cdf0de) to head (7578a15).

Files with missing lines	Patch %	Lines
src/Opc.Ua.Types/BuiltIn/LocalizedText.cs	90.90%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4709      +/-   ##
==========================================
- Coverage   82.85%   82.84%   -0.01%     
==========================================
  Files        2267     2267              
  Lines      345956   345957       +1     
  Branches    60309    60311       +2     
==========================================
- Hits       286640   286625      -15     
- Misses      39219    39238      +19     
+ Partials    20097    20094       -3     

Flag	Coverage Δ
actions	82.84% <90.90%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/Opc.Ua.Types/BuiltIn/LocalizedText.cs	84.85% <90.90%> (-0.30%)	⬇️

... and 33 files with indirect coverage changes

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[Copilot]

🟡 Changes recommended

Encoding-only normalization breaks LocalizedText equality and round-trip consistency.

1 open finding

• Empty text serialization breaks LocalizedText round-trip equality · New

1 resolved since last review

• Nullable buffer assignment fails warnings-as-errors build

🧠 Review effort: Balanced