Use self-background image on someone's profile

Closes #366

src/App.js

@@ -40,7 +40,9 @@ export default {
     this.$i18n.locale = this.$store.state.config.interfaceLanguage
   },
   computed: {
-    currentUser () { return this.$store.state.users.currentUser },
+    currentUser () {
+      return this.selectedUser || this.$store.state.users.currentUser
+    },
     background () {
       return this.currentUser.background_image || this.$store.state.instance.background
     },
@@ -86,6 +88,21 @@ export default {
     unseenNotificationsCount () {
       return this.unseenNotifications.length
     },
+    selectedUser () {
+      if (this.isExternalProfile) {
+        return this.$store.getters.userById(this.$route.params.id)
+      }
+      if (this.isLocalProfile) {
+        return this.$store.getters.userByName(this.$route.params.name)
+      }
+      return null
+    },
+    isExternalProfile () {
+      return this.$route.name === 'external-user-profile'
+    },
+    isLocalProfile () {
+      return this.$route.name === 'user-profile'
+    },
     showFeaturesPanel () { return this.$store.state.instance.showFeaturesPanel }
   },
   methods: {