fix(smtp): allow usehtml to be set in params

[piksel]

Use the configuration updated from props in getHeaders, allowing FromName, FromAddress and UseHTML to be overridden in params.

Fixes #387

[codecov]

Codecov Report

Patch coverage: 85.71% and project coverage change: -0.02% ⚠️

Comparison is base (a59c927) 79.17% compared to head (689c66a) 79.15%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #388      +/-   ##
==========================================
- Coverage   79.17%   79.15%   -0.02%     
==========================================
  Files         102      102              
  Lines        4485     4481       -4     
==========================================
- Hits         3551     3547       -4     
  Misses        756      756              
  Partials      178      178              

Files Changed	Coverage Δ
pkg/services/smtp/smtp.go	89.35% <83.33%> (-0.20%)	⬇️
pkg/services/smtp/smtp_config.go	100.00% <100.00%> (ø)

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