Added better 404 (not found) handling if calling a GetByX method.

[cdmdotnet]

Description

Added better 404 (not found) handling if calling a GetByX method. Returning an exception is messy handling and far from standard pattern handling, in addition to that executing a search for a single well known query is an overkill solution.

Purpose

• [ ] Bugfix (non-breaking change which fixes an issue)
• [x ] New feature (non-breaking change which adds functionality)
• [ x] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• [ ] I have added tests to prove that what I have fixed or added does indeed work
• [x ] I have added documentation as necessary

[Psypher9]

Thank you for this contribution!