add override_instance_wallpaper setting

src/App.js

@@ -76,7 +76,7 @@ export default {
         ? null
         : this.$store.state.instance.background
     },
-    background () { return this.pageBackground || this.userBackground || this.instanceBackground },
+    background () { return this.pageBackground || (this.$store.getters.mergedConfig.overrideInstanceWallpaper && this.userBackground) || this.instanceBackground },
     bgStyle () {
       if (this.background) {
         return {

src/components/settings_modal/tabs/profile_tab.vue

@@ -224,6 +224,11 @@
           />
         </button>
       </div>
+      <BooleanSetting
+        path="overrideInstanceWallpaper"
+      >
+        {{ $t('settings.override_instance_wallpaper') }}
+      </BooleanSetting>
       <p>{{ $t('settings.set_new_profile_background') }}</p>
       <img
         v-if="backgroundPreview"

src/i18n/en.json

@@ -588,6 +588,7 @@
         "hide_user_stats": "Hide user statistics (e.g. the number of followers)",
         "hide_wallpaper": "Hide instance wallpaper",
         "hide_wordfiltered_statuses": "Hide word-filtered posts",
+        "override_instance_wallpaper": "Replace the instance wallpaper with your profile background",
         "import_blocks_from_a_csv_file": "Import blocks from a csv file",
         "import_followers_from_a_csv_file": "Import follows from a csv file",
         "import_mutes_from_a_csv_file": "Import mutes from a csv file",

src/modules/config.js

@@ -122,6 +122,7 @@ export const defaultState = {
   supportedTranslationLanguages: {}, // instance default
   userProfileDefaultTab: 'statuses',
   useBlurhash: true,
+  overrideInstanceWallpaper: false,
 }
 
 // caching the instance default properties