ENH: Add emailer for fixed line testing affected flavors

[AlexCK-STFC]

Description:

Note: Dates are hard-coded, while flavors are customisable.

This is because:

• The dates are unlikely to change
• It would be a pain to make them customisable from the format of the template

Also adds a helper "Print Email" debug function to the emailer

Special Notes:

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Submitter:

Have you (where applicable):

• Added unit tests?
• Checked the latest commit runs on Dev?
• Updated the example config file(s) and README?

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Reviewer

Does this PR:

• Place non-StackStorm code into the lib directory?
• Have unit tests for the action/sensor and lib layers?
• Have clear and obvious action parameter names and descriptions?

[AlexCK-STFC]

Draft until I add unit tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (c54c341) to head (67f330f).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #389   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files          105       106    +1     
  Lines         2468      2534   +66     
  Branches       356       371   +15     
=========================================
+ Hits          2468      2534   +66     

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[anish-mudaraddi]

Tempted to close this and reopen if we need it later

[AlexCK-STFC]

Tempted to close this and reopen if we need it later

Shall we just merge to get the code in? The action won't run unless people run it.

I add the print_email func in this PR too, which would be nice-to-have for other actions

I can always split that off though

[anish-mudaraddi]

maybe set the action to enabled: false - so people won't use it