feat: adapt send_email.py from spook

[kelly-sovacool]

Changes

Originally written for sending reports, but now making it more general so we can eventually use it to send slurm job status updates from biowulf.

Issues

see also https://github.com/CCBR/spook/pull/42

PR Checklist

(Strikethrough any points that are not applicable.)

• This comment contains a description of changes with justifications, with any relevant issues linked.
• Write unit tests for any new features, bug fixes, or other code changes.
• Update docs if there are any API changes.
• Update CHANGELOG.md with a short description of any user-facing changes and reference the PR number. Guidelines: https://keepachangelog.com/en/1.1.0/

[codecov]

Codecov Report

Attention: Patch coverage is 93.10345% with 2 lines in your changes missing coverage. Please review.

Project coverage is 33.92%. Comparing base (8792f5a) to head (e55eb8e).

Files with missing lines	Patch %	Lines
src/ccbr_tools/send_email.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   32.41%   33.92%   +1.51%     
==========================================
  Files          17       18       +1     
  Lines        1265     1294      +29     
==========================================
+ Hits          410      439      +29     
  Misses        855      855              

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