Improve error message when duplicate controllers found

[bkoelman]

Improve error message when duplicate controllers are found, to include the fully qualified type names of the conflicting controllers. This makes it easier for JADNC consumers to root-cause the conflict.

Closes #1188.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

Merging #1193 (3996cc4) into master (79d918a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 3996cc4 differs from pull request most recent head 1dc249b. Consider uploading reports for the commit 1dc249b to get more accurate results

@@           Coverage Diff           @@
##           master    #1193   +/-   ##
=======================================
  Coverage   92.59%   92.59%           
=======================================
  Files         242      242           
  Lines        7706     7707    +1     
=======================================
+ Hits         7135     7136    +1     
  Misses        571      571           

Impacted Files	Coverage Δ
...iDotNetCore/Middleware/JsonApiRoutingConvention.cs	92.06% <100.00%> (+0.12%)	⬆️

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