improve error for schema name validation

[rohityadav1993]

refactor

Addresses: #14511 (comment)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 63.88%. Comparing base (59551e4) to head (c01f5dd).
Report is 1378 commits behind head on master.

Files with missing lines	Patch %	Lines
...ller/api/resources/PinotSchemaRestletResource.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #14517      +/-   ##
============================================
+ Coverage     61.75%   63.88%   +2.13%     
- Complexity      207     1570    +1363     
============================================
  Files          2436     2673     +237     
  Lines        133233   146784   +13551     
  Branches      20636    22509    +1873     
============================================
+ Hits          82274    93770   +11496     
- Misses        44911    46096    +1185     
- Partials       6048     6918     +870     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (+99.99%)	⬆️
integration	100.00% <ø> (+99.99%)	⬆️
integration1	100.00% <ø> (+99.99%)	⬆️
integration2	0.00% <ø> (ø)
java-11	63.83% <0.00%> (+2.12%)	⬆️
java-21	63.75% <0.00%> (+2.13%)	⬆️
skip-bytebuffers-false	63.85% <0.00%> (+2.10%)	⬆️
skip-bytebuffers-true	63.73% <0.00%> (+36.01%)	⬆️
temurin	63.88% <0.00%> (+2.13%)	⬆️
unittests	63.87% <0.00%> (+2.13%)	⬆️
unittests1	55.57% <ø> (+8.68%)	⬆️
unittests2	34.57% <0.00%> (+6.84%)	⬆️

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