Make login failure translateable, translate 'login.failure' to german and english

webapp/components/LoginForm/LoginForm.vue

@@ -98,7 +98,7 @@ export default {
         this.$toast.success(this.$t('login.success'))
         this.$emit('success')
       } catch (err) {
-        this.$toast.error(err.message)
+        this.$toast.error(this.$t('login.failure'))
       }
     },
   },

webapp/locales/de.json

@@ -112,7 +112,8 @@
     "moreInfoURL": "https://human-connection.org",
     "moreInfoHint": "zur Präsentationsseite",
     "hello": "Hallo",
-    "success": "Du bist eingeloggt!"
+    "success": "Du bist eingeloggt!",
+    "failure": "Login fehlgeschlagen"
   },
   "editor": {
     "placeholder": "Schreib etwas Inspirierendes …",

webapp/locales/en.json

@@ -113,7 +113,8 @@
     "moreInfoURL": "https://human-connection.org/en/",
     "moreInfoHint": "to the presentation page",
     "hello": "Hello",
-    "success": "You are logged in!"
+    "success": "You are logged in!",
+    "failure": "Login failed"
   },
   "editor": {
     "placeholder": "Leave your inspirational thoughts …",