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

[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 67.31%. Comparing base (4f7957f) to head (2c69414).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5953   +/-   ##
=========================================
  Coverage     67.31%   67.31%           
  Complexity     4570     4570           
=========================================
  Files           620      620           
  Lines         17147    17147           
  Branches       3312     3312           
=========================================
  Hits          11543    11543           
  Misses         5150     5150           
  Partials        454      454           

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