Fix sonar warnings in TemplatePersistenceManagerFactory

[darshanasbg]

Proposed changes in this pull request

$subject.

Based on the above analysis,

• Reduced code duplication
• Improved method comments
• Removed implementation specific method from the factory.

When should this PR be merged

Immediate

Follow up actions

N/A

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 17.14%. Comparing base (f8429eb) to head (834b2fd).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
...bon/email/mgt/NotificationTemplateManagerImpl.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #277      +/-   ##
============================================
+ Coverage     17.02%   17.14%   +0.11%     
- Complexity      179      180       +1     
============================================
  Files            53       53              
  Lines          3042     3027      -15     
  Branches        335      332       -3     
============================================
+ Hits            518      519       +1     
+ Misses         2483     2467      -16     
  Partials         41       41              

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