Detect mime type when picking a file

The file picker will now try to detect the mime type of the selected file.
If it cannot be detected, it will fallback to `application/octet-stream`.

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenter.kt

@@ -165,8 +165,8 @@ class MessageComposerPresenter(
         val galleryMediaPicker = mediaPickerProvider.registerGalleryPicker { uri, mimeType ->
             handlePickedMedia(uri, mimeType)
         }
-        val filesPicker = mediaPickerProvider.registerFilePicker(AnyMimeTypes) { uri ->
+        val filesPicker = mediaPickerProvider.registerFilePicker(AnyMimeTypes) { uri, mimeType ->
-            handlePickedMedia(uri, MimeTypes.OctetStream)
+            handlePickedMedia(uri, mimeType ?: MimeTypes.OctetStream)
         }
         val cameraPhotoPicker = mediaPickerProvider.registerCameraPhotoPicker { uri ->
             handlePickedMedia(uri, MimeTypes.Jpeg)

libraries/mediapickers/api/src/main/kotlin/io/element/android/libraries/mediapickers/api/PickerProvider.kt

@@ -25,7 +25,7 @@ interface PickerProvider {
     @Composable
     fun registerFilePicker(
         mimeType: String,
-        onResult: (Uri?) -> Unit
+        onResult: (uri: Uri?, mimeType: String?) -> Unit,
     ): PickerLauncher<String, Uri?>
 
     @Composable

libraries/mediapickers/impl/src/main/kotlin/io/element/android/libraries/mediapickers/impl/DefaultPickerProvider.kt

@@ -88,13 +88,16 @@ class DefaultPickerProvider(
     @Composable
     override fun registerFilePicker(
         mimeType: String,
-        onResult: (Uri?) -> Unit,
+        onResult: (uri: Uri?, mimeType: String?) -> Unit,
     ): PickerLauncher<String, Uri?> {
         // Tests and UI preview can't handle Context or FileProviders, so we might as well disable the whole picker
         return if (LocalInspectionMode.current) {
-            NoOpPickerLauncher { onResult(null) }
+            NoOpPickerLauncher { onResult(null, null) }
         } else {
-            rememberPickerLauncher(type = PickerType.File(mimeType)) { uri -> onResult(uri) }
+            rememberPickerLauncher(type = PickerType.File(mimeType)) { uri ->
+                val pickedMimeType = uri?.let { context.contentResolver.getType(it) }
+                onResult(uri, pickedMimeType)
+            }
         }
     }
 

libraries/mediapickers/test/src/main/kotlin/io/element/android/libraries/mediapickers/test/FakePickerProvider.kt

@@ -30,8 +30,8 @@ class FakePickerProvider : PickerProvider {
     }
 
     @Composable
-    override fun registerFilePicker(mimeType: String, onResult: (Uri?) -> Unit): PickerLauncher<String, Uri?> {
+    override fun registerFilePicker(mimeType: String, onResult: (Uri?, String?) -> Unit): PickerLauncher<String, Uri?> {
-        return NoOpPickerLauncher { onResult(result) }
+        return NoOpPickerLauncher { onResult(result, this.mimeType) }
     }
 
     @Composable