r.category: Add color option

[NishantBansal2003]

Enhancement: Add Color Option to Category Output

Fixes: #4071

Overview

This PR introduces a new color option for r.category, allowing users to retrieve category colors alongside labels. This enhancement is useful for visualization workflows where knowing both the category label and its associated color is important.

Changes Made

• Added a color option that allows specifying the output format:
  • none (default) – No color output.
  • rgb – Outputs colors in rgb(r, g, b) format.
  • hex – Outputs colors in #RRGGBB format.
  • triplet – Outputs colon-separated R:G:B values.
• Updated PLAIN output format to include color:

  1 trees, very green rgb(68, 1, 84)
  2 water, very deep rgb(253, 231, 37)
  

• Updated JSON output format to include color:

  [
      {
          "category": 1,
          "description": "trees, very green",
          "color": "rgb(68, 1, 84)"
      },
      {
          "category": 2,
          "description": "water, very deep",
          "color": "rgb(253, 231, 37)"
      }
  ]

Testing & Validation

• Existing feature tests were taken from the r.category doctest file.
• New feature tests for the color option have been added at the end.

[petrasovaa]

Again, I would make sure you can't reuse some of the functions from the library you wrote. Maybe it's not possible, but it would be nice to avoid code duplication.

[NishantBansal2003]

Sure, I will keep that in mind.

[petrasovaa]

Thank you, this looks great, just couple comments.

[petrasovaa]

Did you have actual issues with this when you ran the tests on windows? That's why the replace is there?

[NishantBansal2003]

Yes, I tested this, and pytest was failing on Windows with an error similar to this for each test:

FAILED raster/r.category/tests/r_category_test.py::test_r_category_plain_output - AssertionError: Expected 1,trees
  2,water
  , but got 1,trees

  2,water

  
assert '1,trees\r\n2,water\r\n' == '1,trees\n2,water\n'
  
  - 1,trees
  + 1,trees

  ?        +
  - 2,water
  + 2,water

  ?        +

[wenzeslaus]

Perhaps we should just read it internally with text mode (aka universal newlines) to avoid the issues at this level.

[echoix]

Perhaps we should just read it internally with text mode (aka universal newlines) to avoid the issues at this level.

See #4517?