Add Odd-Even Merge operation mode (#1445)

* Add ODD_EVEN_MERGE sort type

* Add process method to merge odd and even PDF pages

* Add test cases for Odd-Even merge method

* Add Odd-Even Merge mode in PDF Organizer webpage

This also add a new translatable text message variable pdfOrganiser.mode.10 with translation for english and german

* Add ODD_EVEN_MERGE documentation to RearrangePagesRequest

* Add english translation for pdfOrganiser.mode.10

---------

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

src/test/java/stirling/software/SPDF/controller/api/RearrangePagesPDFControllerTest.java

@@ -0,0 +1,82 @@
+package stirling.software.SPDF.controller.api;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class RearrangePagesPDFControllerTest {
+
+    /**
+     * Tests the behavior of the oddEvenMerge method when there are no pages in the document.
+     */
+    @Test
+    void oddEvenMerge_noPages() {
+        RearrangePagesPDFController sut = new RearrangePagesPDFController();
+        int totalNumberOfPages = 0;
+
+        List<Integer> newPageOrder = sut.oddEvenMerge(totalNumberOfPages);
+
+        assertNotNull(newPageOrder, "Returning null instead of page order list");
+        assertEquals(List.of(), newPageOrder, "Page order doesn't match");
+    }
+
+    /**
+     * Tests the behavior of the oddEvenMerge method when there are odd total pages in the document.
+     */
+    @Test
+    void oddEvenMerge_oddTotalPageNumber() {
+        RearrangePagesPDFController sut = new RearrangePagesPDFController();
+        int totalNumberOfPages = 5;
+
+        List<Integer> newPageOrder = sut.oddEvenMerge(totalNumberOfPages);
+
+        assertNotNull(newPageOrder, "Returning null instead of page order list");
+        assertEquals(Arrays.asList(0,3,1,4,2), newPageOrder, "Page order doesn't match");
+    }
+
+    /**
+     * Tests the behavior of the oddEvenMerge method when there are even total pages in the document.
+     */
+    @Test
+    void oddEvenMerge_evenTotalPageNumber() {
+        RearrangePagesPDFController sut = new RearrangePagesPDFController();
+        int totalNumberOfPages = 6;
+
+        List<Integer> newPageOrder = sut.oddEvenMerge(totalNumberOfPages);
+
+        assertNotNull(newPageOrder, "Returning null instead of page order list");
+        assertEquals(Arrays.asList(0,3,1,4,2,5), newPageOrder, "Page order doesn't match");
+    }
+
+    /**
+     * Tests the behavior of the oddEvenMerge method with multiple test cases of multiple pages.
+     * @param totalNumberOfPages The total number of pages in the document.
+     * @param expectedPageOrder The expected order of the pages after rearranging.
+     */
+    @ParameterizedTest
+    @CsvSource({
+            "1, '0'",
+            "2, '0,1'",
+            "3, '0,2,1'",
+            "4, '0,2,1,3'",
+            "5, '0,3,1,4,2'",
+            "6, '0,3,1,4,2,5'",
+            "10, '0,5,1,6,2,7,3,8,4,9'",
+            "50, '0,25,1,26,2,27,3,28,4,29,5,30,6,31,7,32,8,33,9,34,10,35," +
+                    "11,36,12,37,13,38,14,39,15,40,16,41,17,42,18,43,19,44,20,45,21,46," +
+                    "22,47,23,48,24,49'"
+    })
+    void oddEvenMerge_multi_test(int totalNumberOfPages, String expectedPageOrder) {
+        RearrangePagesPDFController sut = new RearrangePagesPDFController();
+
+        List<Integer> newPageOrder = sut.oddEvenMerge(totalNumberOfPages);
+
+        assertNotNull(newPageOrder, "Returning null instead of page order list");
+        assertEquals(Arrays.stream(expectedPageOrder.split(",")).map(Integer::parseInt).toList(), newPageOrder, "Page order doesn't match");
+    }
+}