ENH: Parachute trigger doesn't work if "Apogee" is used instead of "apogee"

[Gui-FernandesBR]

Pull request type

• Code maintenance (refactoring, formatting, tests)

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally
• CHANGELOG.md has been updated (if relevant)

Current behavior

• The parachute trigger option "apogee" is case sensitive, so the triggerfunc is not set if you use "Apogee" or "APOGEE" instead of the expoected "apogee" value.
• Worse is that the Parachute class doesn't raise any error is the user pass a string like "Apogee" or "AnyOtherThing", so the user just gets an error message when simulating the Flight class

New behavior

• Refactor the Parachute class init just a bit.
• Using the built-in lower() method to compare the string without being case-sensitive.
• You're gonna know if the triggerfunc cannot be set after initializing the Parachute class.

Breaking change

• No

Additional information

Reported by jackson.dendy on discord tonight, from the univ of Tenesse.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (0ef9849) 70.91% compared to head (c1e43ec) 70.90%.
Report is 11 commits behind head on develop.

❗ Current head c1e43ec differs from pull request most recent head a6dfea3. Consider uploading reports for the commit a6dfea3 to get more accurate results

Files	Patch %	Lines
rocketpy/rocket/parachute.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #489      +/-   ##
===========================================
- Coverage    70.91%   70.90%   -0.01%     
===========================================
  Files           55       55              
  Lines         9261     9263       +2     
===========================================
+ Hits          6567     6568       +1     
- Misses        2694     2695       +1     

Flag	Coverage Δ
unittests	70.90% <75.00%> (-0.01%)	⬇️

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[giovaniceotto]

Great fix.

Improvement suggestion: line 129 of rocketpy/rocket/parachute.py

- The string "apogee," which triggers the parachute at apogee, i.e.,  when the rocket reaches its highest point and starts descending.

I believe we should change from "apogee," to "apogee",.