Allow specify products to notify

[adybbroe]

This PR adds an option to allow specifying in the configuration which (national) products should trigger notifications

• Closes #xxxx
• Tests added
• Tests passed: Passes pytest
• Passes flake8
• Fully documented

[codecov-commenter]

Codecov Report

Merging #19 (1835753) into main (21c7a1a) will increase coverage by 0.24%.
The diff coverage is 95.34%.

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@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
+ Coverage   80.94%   81.19%   +0.24%     
==========================================
  Files          21       21              
  Lines        2299     2340      +41     
  Branches      350      362      +12     
==========================================
+ Hits         1861     1900      +39     
- Misses        406      408       +2     
  Partials       32       32              

Flag	Coverage Δ
unittests	81.19% <95.34%> (+0.24%)	⬆️

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Files Changed	Coverage Δ
activefires_pp/tests/test_messaging.py	100.00% <ø> (ø)
activefires_pp/fire_notifications.py	38.96% <81.81%> (+1.24%)	⬆️
activefires_pp/tests/test_fire_notifications.py	99.11% <100.00%> (+0.34%)	⬆️

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[coveralls]

coverage: 82.564% (+0.2%) from 82.34% when pulling 1835753 on allow-specify-products-to-notify into 21c7a1a on main.

[mraspaud]

LGTM

[mraspaud]

@adybbroe I'll let you fix the merge conflicts