Add KDoc to six small library API modules

Cover the remaining interfaces of libraries/troubleshoot, libraries/matrixmedia,
libraries/dateformatter, libraries/featureflag, libraries/workmanager and
libraries/mediaviewer, along with their members and parameters.

Behaviours worth recording: NotificationTroubleshootTest reports its outcome
through its state flow rather than by returning, and its quickFix throws unless
the test offers one; DateFormatter.format turns a null timestamp into an empty
string so callers need no null check; ImageLoaderHolder keeps one loader per
session because decrypting room media needs that session's client.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

libraries/mediaviewer/api/src/main/kotlin/io/element/android/libraries/mediaviewer/api/local/LocalMediaFactory.kt

@@ -12,9 +12,15 @@ import android.net.Uri
 import io.element.android.libraries.matrix.api.media.MediaFile
 import io.element.android.libraries.mediaviewer.api.MediaInfo
 
+/**
+ * Builds the [LocalMedia] the media viewer renders, from either a downloaded Matrix media file or an arbitrary content uri.
+ */
 interface LocalMediaFactory {
     /**
      * This method will create a [LocalMedia] with the given [MediaFile] and [MediaInfo].
+     *
+     * @param mediaFile the file already downloaded from the homeserver.
+     * @param mediaInfo what is known about the media from the event that carried it.
      */
     fun createFromMediaFile(
         mediaFile: MediaFile,
@@ -24,6 +30,11 @@ interface LocalMediaFactory {
     /**
      * This method will create a [LocalMedia] with the given mimeType, name and formattedFileSize
      * If any of those params are null, it'll try to read them from the content.
+     *
+     * @param uri the content to display, for instance one just picked by the user.
+     * @param mimeType the MIME type, or `null` to read it from the content.
+     * @param name the file name, or `null` to read it from the content.
+     * @param formattedFileSize the size to display, or `null` to read it from the content.
      */
     fun createFromUri(
         uri: Uri,

libraries/mediaviewer/api/src/main/kotlin/io/element/android/libraries/mediaviewer/api/local/LocalMediaRenderer.kt

@@ -10,7 +10,15 @@ package io.element.android.libraries.mediaviewer.api.local
 
 import androidx.compose.runtime.Composable
 
+/**
+ * Renders a media file held on the device, picking the right player or viewer for its type.
+ */
 interface LocalMediaRenderer {
+    /**
+     * Draws the media, filling the space it is given.
+     *
+     * @param localMedia the file to display, along with what is known about its type.
+     */
     @Composable
     fun Render(localMedia: LocalMedia)
 }

libraries/mediaviewer/api/src/main/kotlin/io/element/android/libraries/mediaviewer/api/util/FileExtensionExtractor.kt

@@ -8,6 +8,13 @@
 
 package io.element.android.libraries.mediaviewer.api.util
 
+/**
+ * Extracts the extension of a file name, so it can be shown to the user and used to pick an icon.
+ */
 interface FileExtensionExtractor {
+    /**
+     * @param name the file name to inspect.
+     * @return the extension without its dot, or an empty string when the name has none.
+     */
     fun extractFromName(name: String): String
 }