frontend/Story.vue: disable editable switch if user is guest

Pass camp as function instead of object into campRoleMixin.

Issue: ecamp#1415

frontend/src/mixins/campRoleMixin.js

@@ -4,18 +4,24 @@ export const campRoleMixin = {
       return this.isMember || this.isManager
     },
     isGuest () {
-      return this.camp?.role === 'guest'
+      return this.role === 'guest'
     },
     isManager () {
-      return this.camp?.role === 'manager'
+      return this.role === 'manager'
     },
     isMember () {
-      return this.camp?.role === 'member'
+      return this.role === 'member'
+    },
+    role () {
+      if (typeof this.camp === 'function') {
+        return this.camp()?.role
+      }
+      return this.camp?.role
     }
   },
   mounted () {
-    if (typeof this.camp !== 'object') {
-      throw new Error('User of the campRoleMixin must expose a method/proxy camp()')
+    if (typeof this.camp !== 'object' && typeof this.camp !== 'function') {
+      throw new Error('User of the campRoleMixin must expose a camp as object proxy or function')
     }
   }
 }

frontend/src/views/camp/Story.vue

@@ -8,6 +8,7 @@ Admin screen of a camp: Displays details & periods of a single camp and allows t
       <template v-if="$vuetify.breakpoint.smAndUp">
         <e-switch v-model="editing" :label="$tc('global.button.editable')"
                   class="ec-story-editable ml-auto"
+                  :disabled="!isContributor"
                   @click="$event.preventDefault()" />
       </template>
       <v-menu v-else offset-y>
@@ -60,6 +61,7 @@ Admin screen of a camp: Displays details & periods of a single camp and allows t
 <script>
 import ContentCard from '@/components/layout/ContentCard.vue'
 import StoryPeriod from '@/components/camp/StoryPeriod.vue'
+import { campRoleMixin } from '@/mixins/campRoleMixin'
 
 const PRINT_SERVER = window.environment.PRINT_SERVER
 
@@ -69,6 +71,7 @@ export default {
     StoryPeriod,
     ContentCard
   },
+  mixins: [campRoleMixin],
   props: {
     camp: { type: Function, required: true }
   },