feat(server): custom library scanning interval (#4390)

* add automatic library scan config options

* add validation

* open api

* use CronJob instead of cron-validator

* fix tests

* catch potential error of the library scan initialization

* better description for input field

* move library scan job initialization to server app service

* fix tests

* add comments to all parameters of cronjob contructor

* make scan a child of a more general library object

* open api

* chore: cleanup

* move cronjob handling to job repoistory

* web: select for common cron expressions

* fix open api

* fix tests

* put scanning settings in nested accordion

* fix system config validation

* refactor, tests

---------

Co-authored-by: Jason Rasmussen <jrasm91@gmail.com>

server/src/infra/entities/system-config.entity.ts

@@ -94,6 +94,9 @@ export enum SystemConfigKey {
   TRASH_DAYS = 'trash.days',
 
   THEME_CUSTOM_CSS = 'theme.customCss',
+
+  LIBRARY_SCAN_ENABLED = 'library.scan.enabled',
+  LIBRARY_SCAN_CRON_EXPRESSION = 'library.scan.cronExpression',
 }
 
 export enum TranscodePolicy {
@@ -232,4 +235,10 @@ export interface SystemConfig {
   theme: {
     customCss: string;
   };
+  library: {
+    scan: {
+      enabled: boolean;
+      cronExpression: string;
+    };
+  };
 }