Add documentation and test for EditorLauncherParams field mapping

Ensures all EditorLauncherParams fields are handled in EditorLauncher.addEditorExtras()
through documentation and a unit test that validates completeness.

Changes:
- Add cross-reference documentation in EditorLauncherParams and EditorLauncher
- Add EditorLauncherTest with detailed field-to-method mapping documentation
- Test validates that all fields are accounted for in addEditorExtras methods
- Filter out Kotlin synthetic fields in test validation

Author: oguzkocer

WordPress/src/main/java/org/wordpress/android/ui/posts/EditorLauncher.kt

@@ -72,6 +72,9 @@ class EditorLauncher @Inject constructor(
 
     /**
      * Adds all editor parameters as Intent extras.
+     * 
+     * Each field in EditorLauncherParams must be handled by one of the add*Extras methods.
+     * See EditorLauncherTest for complete field-to-method mapping documentation.
      */
     private fun Intent.addEditorExtras(params: EditorLauncherParams) {
         addBasicExtras(params)

WordPress/src/main/java/org/wordpress/android/ui/posts/EditorLauncherParams.kt

@@ -9,6 +9,9 @@ import org.wordpress.android.ui.posts.PostUtils.EntryPoint
  *
  * This data class replaces the Bundle-based approach with named parameters in Kotlin
  * and provides a builder pattern for Java compatibility.
+ *
+ * All fields are mapped to Intent extras in EditorLauncher.addEditorExtras().
+ * See EditorLauncherTest for field-to-method mapping documentation.
  */
 data class EditorLauncherParams(
     val site: SiteModel,

WordPress/src/test/java/org/wordpress/android/ui/posts/EditorLauncherTest.kt

@@ -0,0 +1,60 @@
+package org.wordpress.android.ui.posts
+
+import org.junit.Test
+import org.junit.Assert.assertEquals
+
+class EditorLauncherTest {
+    @Test
+    fun `all EditorLauncherParams fields should be handled in addEditorExtras`() {
+        // This test ensures that every field in EditorLauncherParams is handled by one of the
+        // add*Extras methods in EditorLauncher. When adding new fields to EditorLauncherParams,
+        // you must update both this test and the corresponding add*Extras method.
+
+        val handledFields = setOf(
+            // addBasicExtras()
+            "site",           // -> WordPress.SITE
+            "isPage",         // -> EditPostActivityConstants.EXTRA_IS_PAGE
+            "isPromo",        // -> EditPostActivityConstants.EXTRA_IS_PROMO
+
+            // addPostExtras()
+            "postLocalId",    // -> EditPostActivityConstants.EXTRA_POST_LOCAL_ID
+            "postRemoteId",   // -> EditPostActivityConstants.EXTRA_POST_REMOTE_ID
+            "loadAutoSaveRevision", // -> EditPostActivityConstants.EXTRA_LOAD_AUTO_SAVE_REVISION
+            "isQuickPress",   // -> EditPostActivityConstants.EXTRA_IS_QUICKPRESS
+            "isLandingEditor", // -> EditPostActivityConstants.EXTRA_IS_LANDING_EDITOR
+            "isLandingEditorOpenedForNewSite", // -> EditPostActivityConstants.EXTRA_IS_LANDING_EDITOR_OPENED_FOR_NEW_SITE
+
+            // addReblogExtras()
+            "reblogPostTitle", // -> EditPostActivityConstants.EXTRA_REBLOG_POST_TITLE
+            "reblogPostQuote", // -> EditPostActivityConstants.EXTRA_REBLOG_POST_QUOTE
+            "reblogPostImage", // -> EditPostActivityConstants.EXTRA_REBLOG_POST_IMAGE
+            "reblogPostCitation", // -> EditPostActivityConstants.EXTRA_REBLOG_POST_CITATION
+            "reblogAction",   // -> Intent.setAction()
+
+            // addPageExtras()
+            "pageTitle",      // -> EditPostActivityConstants.EXTRA_PAGE_TITLE
+            "pageContent",    // -> EditPostActivityConstants.EXTRA_PAGE_CONTENT
+            "pageTemplate",   // -> EditPostActivityConstants.EXTRA_PAGE_TEMPLATE
+
+            // addMiscExtras()
+            "voiceContent",   // -> EditPostActivityConstants.EXTRA_VOICE_CONTENT
+            "insertMedia",    // -> EditPostActivityConstants.EXTRA_INSERT_MEDIA
+            "source",         // -> AnalyticsUtils.EXTRA_CREATION_SOURCE_DETAIL
+            "promptId",       // -> EditPostActivityConstants.EXTRA_PROMPT_ID
+            "entryPoint"      // -> EditPostActivityConstants.EXTRA_ENTRY_POINT
+        )
+
+        val actualFields = EditorLauncherParams::class.java.declaredFields
+            .filter { !it.isSynthetic && !it.name.contains("$") } // Filter out Kotlin synthetic fields
+            .map { it.name }
+            .toSet()
+
+        assertEquals(
+            "All EditorLauncherParams fields must be handled in addEditorExtras(). " +
+                    "Missing: ${actualFields - handledFields}, " +
+                    "Extra: ${handledFields - actualFields}",
+            handledFields,
+            actualFields
+        )
+    }
+}