Extensions, Automated Router Registration, Better updateListing validation and Type Hints

[Prakhar896]

Overview:

• New Extensions "service" with static method functionality, added a method that makes filtering dictionaries easier
• New index.js in routes which auto-detects all router files, regardless of file tree depth, to collate and associate them with paths in a singular object. This object is used in ./index.js to automatically register routes
• Automated route registration will only activate should you set routerRegistration to true in your configuration in config/config.json
• Fixed type hints in models/index.js, type hints are now fully accurate. models/index.js will hard-import models to force intellisense capabilities. Other models defined will be imported to but won't have intellisense functionality
• Improved validation in /updateListing via a yup validation schema

No sensitive changes in this PR except for the if condition check in ./index.js that checks if routerRegistration is automated.