Improve code coverage

[Acconut]

• Remove unused Template.MarshalJSON function
• Add tests for notifications APIs

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.09%. Comparing base (830730d) to head (8c0311c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   77.73%   81.09%   +3.36%     
==========================================
  Files           6        6              
  Lines         467      455      -12     
==========================================
+ Hits          363      369       +6     
+ Misses         77       58      -19     
- Partials       27       28       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.