Add example for AAD Service Principal connection

[RudraNirvan]

Fixes #23.

@shueybubbles opened after addressing comments for #25.

[ghost]

All CLA requirements met.

[codecov-commenter]

Codecov Report

Merging #27 (79532e0) into main (f21bac1) will decrease coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
- Coverage   71.28%   71.17%   -0.12%     
==========================================
  Files          24       24              
  Lines        5418     5418              
==========================================
- Hits         3862     3856       -6     
- Misses       1311     1315       +4     
- Partials      245      247       +2     

Impacted Files	Coverage Δ
tds.go	65.13% <0.00%> (-0.73%)	⬇️

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