Added Scheduled Job for adding missing screenshot urls of scrapable bookmarks

[pisal-shubham]

Issue number: resolves #173

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Checklist

• [x] Code Formatter (run prettier/spotlessApply)
• [x] Code has unit tests? (If no explain in _otherinformation)
• [x] Builds on localhost
• [x] Builds/Runs in docker compose

What is the current behavior?

What is the new behavior?

• A method to fetch bookmarks with empty or null screenshot_urls is added in bookmark repository
• Added scheduled job in bookmark service which fetches the list of bookmarks having missing urls and if the bookmark is scrapable the screenshot_url is generated and stored in bookmark.

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Other information

• Added methods to TenantAspect class to run before methods annotated with @Scheduled annotation. The aspect methods perform following tasks.:
  1. Add authentication in security context with SUPERUSER.
  2. Disable TenantEntityListner.
  3. Add callback function to clear security context and enable TenantEntityListner after current transaction is completed.
• Added methods to enable and disable TenantEntityListner and added logic to do nothing in preupdate, prepersist, preremove methods if TenantEntityListner is disabled.
• Modified logic to enable TenantFilter base on SUPERUSER_ID in tenant context.
• Enabled Scheduling by adding @EnableScheduling annotation in FindFirstApplication class