refactor: change type of exceptionMessage to string

Author: Melissa Mazura

app/src/main/java/fr/free/nrw/commons/contributions/Contribution.kt

@@ -30,7 +30,7 @@ data class Contribution constructor(
     var chunkInfo: ChunkInfo? = null,
     // add error message to keep track of error message for failed upload
     var errorMessage: String? = null,
-    var exceptionMessage: Exception? = null,
+    var exceptionMessage: String? = null,
     /**
      * @return array list of entityids for the depictions
      */

app/src/main/java/fr/free/nrw/commons/upload/worker/UploadWorker.kt

@@ -407,7 +407,7 @@ class UploadWorker(var appContext: Context, workerParams: WorkerParameters) :
                         if (contribution.errorMessage == null) {
                             contribution.errorMessage = "upload from stash failed with exception"
                         }
-                        contribution.exceptionMessage = exception
+                        contribution.exceptionMessage = exception.toString()
                         Timber.e(exception)
                         Timber.e("Upload from stash failed for contribution : $filename")
                         showFailedNotification(contribution)
@@ -446,7 +446,7 @@ class UploadWorker(var appContext: Context, workerParams: WorkerParameters) :
             if (contribution.errorMessage == null) {
                 contribution.errorMessage = "upload to stash failed with exception"
             }
-            contribution.exceptionMessage = exception
+            contribution.exceptionMessage = exception.toString()
             Timber.e(exception)
             Timber.e("Stash upload failed for contribution: $filename")
             showFailedNotification(contribution)