Fix Code QL on ConfigService

[kbeaugrand]

Description

What's new?

• Use dedicated exception handling in ConfigService

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Tests
• Other

[codecov]

Codecov Report

Base: 89.58% // Head: 89.54% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (a582d8a) compared to base (d459bd8).
Patch coverage: 88.88% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1487      +/-   ##
==========================================
- Coverage   89.58%   89.54%   -0.04%     
==========================================
  Files         255      255              
  Lines        8034     8034              
==========================================
- Hits         7197     7194       -3     
- Misses        837      840       +3     

Impacted Files	Coverage Δ
...zureIoTHub.Portal.Server/Services/ConfigService.cs	98.55% <88.88%> (-1.45%)	⬇️

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