Override old JWT on login

android/app/src/main/java/de/hft/geotracker/activities/Login.kt

@@ -80,6 +80,7 @@ class Login : AppCompatActivity() {
                     val headers = response.headers()
                     val authentication = headers.get("Authorization")
 
+                    deleteFile("JWToken")
                     openFileOutput("JWToken", Context.MODE_PRIVATE).use {
                         it.write(authentication!!.toByteArray())
                     }