* refactor: refactor all queries,mutations and subscriptions for shortcode module
* test: rewrote test cases for shortcodes
* chore: modified shortcode error code
* chore: created helper function to do shortcode type conversion in service file
* chore: simplifed logic to fetch user shortcodes with cursor pagination
* chore: removed migrations file
* chore: removed unused imports in shortcodes module
* chore: modified generateUniqueShortCodeID function
* chore: modified generateUniqueShortCodeID function
* chore: changed jwtService to use verify instead of decode
* docs: added teacher comments to all shortcodes service methods
* chore: removed stale test cases from shortcode modules