Feat/email destination changes

[iwilson-oa]

• Adjust email_destination TaskHandler to allow use of TLS/credentials to be optional, and set default port to 587
• Adjust email_destination protocol schema to ensure that smtp_server and sender are set

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.25%. Comparing base (41358b1) to head (50577bb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/opentaskpy/remotehandlers/email.py	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
- Coverage   89.25%   89.25%   -0.01%     
==========================================
  Files          21       21              
  Lines        2486     2494       +8     
==========================================
+ Hits         2219     2226       +7     
- Misses        267      268       +1     

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