GOATS-823 GOATS-824: Add tests for middleware and update TNS message.

[davner]

Checklist

• Added a release note in doc/changes using the PR number.

[codecov]

Codecov Report

❌ Patch coverage is 97.22222% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 76.09%. Comparing base (b194fa5) to head (69e1706).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/goats_tom/middleware/tns.py	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #379      +/-   ##
==========================================
+ Coverage   75.81%   76.09%   +0.27%     
==========================================
  Files         230      230              
  Lines        7171     7203      +32     
  Branches      451      451              
==========================================
+ Hits         5437     5481      +44     
+ Misses       1651     1638      -13     
- Partials       83       84       +1     

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