backup site: add contents

it is a json that can be one of the three:

* null - include everything
* include - only include these ids
* exclude - everything except these ids

src/backuptask.js

@@ -493,6 +493,24 @@ async function downloadMail(backupSite, remotePath, progressCallback) {
     debug('downloadMail: time: %s', (new Date() - startTime)/1000);
 }
 
+function shouldBackup(backupSite, id) {
+    if (!backupSite.contents) return true;
+
+    const { include, exclude } = backupSite;
+
+    if (include && !include.includes(id)) {
+        debug(`fullBackup: skipped backup of ${id} since it is not included`);
+        return false;
+    }
+
+    if (exclude?.includes(id)) {
+        debug(`fullBackup: skipped backup of ${id} since it is not included`);
+        return false;
+    }
+
+    return true;
+}
+
 // this function is called from external process. calling process is expected to have a lock
 async function fullBackup(backupSiteId, options, progressCallback) {
     assert.strictEqual(typeof backupSiteId, 'string');
@@ -518,6 +536,7 @@ async function fullBackup(backupSiteId, options, progressCallback) {
             debug(`fullBackup: skipped backup ${app.fqdn} (${i+1}/${allApps.length}) since automatic backup disabled`);
             continue; // nothing to backup
         }
+        if (!shouldBackup(backupSite, app.id)) continue;
 
         progressCallback({ percent, message: `Backing up ${app.fqdn} (${i+1}/${allApps.length}). Waiting for lock` });
         await locks.wait(`${locks.TYPE_APP_BACKUP_PREFIX}${app.id}`);
@@ -529,6 +548,8 @@ async function fullBackup(backupSiteId, options, progressCallback) {
         if (appBackupId) appBackupIds.push(appBackupId); // backupId can be null if in BAD_STATE and never backed up
     }
 
+    if (!shouldBackup(backupSite, 'mail+platform')) return appBackupIds;
+
     progressCallback({ percent, message: 'Backing up mail' });
     percent += step;
     const mailBackupId = await backupMailWithTag(backupSite, tag, options, (progress) => progressCallback({ percent, message: progress.message }));