Covered Theme module with tests

- Extracted `ColorReplacementGenerator`;
- Extracted `ColorConverterImpl`;
- Added documentation to some classes;
- `hex_to_rgba` now supports shorthand hex colors (#fff).

tests/utils/theme/test_theme_path_provider.py

@@ -0,0 +1,28 @@
+import unittest
+
+from scripts.utils.theme.theme_path_provider import ThemePathProvider
+
+
+class ThemePathProviderTestCase(unittest.TestCase):
+    def setUp(self):
+        self.theme_path_provider = ThemePathProvider()
+
+    def test_get_theme_path_with_valid_values_returns_correct_path(self):
+        themes_folder = "/usr/share/themes"
+        color_name = "Marble"
+        theme_mode = "dark"
+        theme_type = "gnome-shell"
+
+        expected_path = f"{themes_folder}/Marble-{color_name}-{theme_mode}/{theme_type}/"
+        actual_path = self.theme_path_provider.get_theme_path(themes_folder, color_name, theme_mode, theme_type)
+
+        assert expected_path == actual_path
+
+    def test_get_theme_path_with_empty_values_raises_exception(self):
+        themes_folder = ""
+        color_name = ""
+        theme_mode = ""
+        theme_type = ""
+
+        with self.assertRaises(ValueError):
+            self.theme_path_provider.get_theme_path(themes_folder, color_name, theme_mode, theme_type)