refactor: Enhance docs, add more tests in `RSA`

[Hardvan]

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.62%. Comparing base (3de202b) to head (52caad1).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5898      +/-   ##
============================================
+ Coverage     70.60%   70.62%   +0.02%     
- Complexity     4838     4843       +5     
============================================
  Files           648      648              
  Lines         17507    17511       +4     
  Branches       3374     3374              
============================================
+ Hits          12361    12368       +7     
+ Misses         4681     4679       -2     
+ Partials        465      464       -1     

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