MOBILE-3188 Settings: Consistently show total size estimate for site

Changes the two settings pages that show the size of a site (from the
main menu, these are 'App settings / Space usage' and 'Preferences')
so that they:

a) do not show the number of cache entries (not very informative for
   end users)
b) show an estimate for 'space usage' that includes the total size
   of data in ws_cache

The space usage estimate is not perfect (it doesn't include the
per-row overhead in the ws_cache table, or other cached data that
can be deleted such as calendar events or user data) but it will
probably be good enough, and I don't think the 'number of entries'
things was helpful to anyone.

src/classes/site.ts

@@ -1384,6 +1384,29 @@ export class CoreSite {
         }
     }
 
+    /**
+     * Gets an approximation of the cache table usage of the site.
+     *
+     * Currently this is just the total length of the data fields in the cache table.
+     *
+     * @return Promise resolved with the total size of all data in the cache table (bytes)
+     */
+    getCacheUsage(): Promise<number> {
+        return this.db.getFieldSql('SELECT SUM(length(data)) FROM ' + CoreSite.WS_CACHE_TABLE);
+    }
+
+    /**
+     * Gets a total of the file and cache usage.
+     *
+     * @return Promise with the total of getSpaceUsage and getCacheUsage
+     */
+    async getTotalUsage(): Promise<number> {
+        const space = await this.getSpaceUsage();
+        const cache = await this.getCacheUsage();
+
+        return space + cache;
+    }
+
     /**
      * Returns the URL to the documentation of the app, based on Moodle version and current language.
      *

src/core/settings/pages/site/site.html

@@ -33,7 +33,6 @@
                     <ion-item text-wrap *ngIf="spaceUsage">
                         <h2 text-wrap>{{ 'core.settings.spaceusage' | translate }} <ion-icon name="information-circle" color="info" [attr.aria-label]="'core.info' | translate" (click)="showSpaceInfo()"></ion-icon></h2>
                         <p *ngIf="spaceUsage.spaceUsage != null">{{ spaceUsage.spaceUsage | coreBytesToSize }}</p>
-                        <p *ngIf="spaceUsage.cacheEntries != null">{{ 'core.settings.entriesincache' | translate: { $a: spaceUsage.cacheEntries } }}</p>
                         <button ion-button icon-only clear color="danger" item-end (click)="deleteSiteStorage()" [hidden]="!spaceUsage.spaceUsage > '0' && !spaceUsage.cacheEntries > '0'" [attr.aria-label]="'core.settings.deletesitefilestitle' | translate">
                             <ion-icon name="trash"></ion-icon>
                         </button>

src/core/settings/pages/space-usage/space-usage.html

@@ -20,7 +20,6 @@
             <p text-wrap>{{ site.fullName }}</p>
             <div item-end>
                 <p *ngIf="site.spaceUsage != null" text-end>{{ site.spaceUsage | coreBytesToSize }}</p>
-                <p *ngIf="site.cacheEntries != null" text-end>{{ 'core.settings.entriesincache' | translate: { $a: site.cacheEntries } }}</p>
             </div>
             <button ion-button icon-only clear color="danger" item-end (click)="deleteSiteStorage(site)" [hidden]="!site.spaceUsage > '0' && !site.cacheEntries > '0'" [attr.aria-label]="'core.settings.deletesitefilestitle' | translate">
                 <ion-icon name="trash"></ion-icon>
@@ -30,7 +29,6 @@
             <h2>{{ 'core.settings.total' | translate }}</h2>
             <div item-end>
                 <p>{{ totals.spaceUsage | coreBytesToSize }}</p>
-                <p>{{ 'core.settings.entriesincache' | translate: { $a: totals.cacheEntries } }}</p>
             </div>
         </ion-item-divider>
     </core-loading>

src/core/settings/providers/helper.ts

@@ -34,7 +34,7 @@ import { TranslateService } from '@ngx-translate/core';
  */
 export interface CoreSiteSpaceUsage {
     cacheEntries?: number; // Number of cached entries that can be cleared.
-    spaceUsage?: number; // Space used in this site.
+    spaceUsage?: number; // Space used in this site (total files + estimate of cache).
 }
 
 /**
@@ -154,7 +154,7 @@ export class CoreSettingsHelper {
 
         await Promise.all([
             this.calcSiteClearRows(site).then((rows) => siteInfo.cacheEntries = rows),
-            site.getSpaceUsage().then((size) => siteInfo.spaceUsage = size),
+            site.getTotalUsage().then((size) => siteInfo.spaceUsage = size),
         ]);
 
         return siteInfo;