Converting Existing PHP with Codeigniter Framework to (SaaS) for multi-tenant / multi-merchant with Subscription

We need a web-app which is a single tenant to be converted to (SaaS) for multi-tenant / multi-merchant. This application will be in the form of Software as a Service (SaaS), where the multi-tenant / multi-merchant can purchase a subscription package, monthly to use the system, if thye dont py, then their usage is suspended, and they are informed of this. We already have the application (along with its source code) which would roughly correspond to the web-app I wanted, we need a freelancer to make modifications to the application. The application that will be the basis of this project is the Stock Manager Advance Tecdiary This application was only designed for single tenant / merchant / owner (single app). In the application, the tenant / merchant represent by owner role (please look the app first). OBJECTIVE: 1. WE want the SAAS version to be developed based on the Multiple database, single code-base method. where when a merchant register, the system creates a separate database for every merchant with No modification to the existing single-tenant codebase. 2)We need the system to create sub-domains for each regitered merchant, if the site is [login to view URL], then when a client registers, they will be assigned a URL like [login to view URL], [login to view URL] etc. To make our app SaaS friendly we need to check the sub-domain and then accordingly connect to a database. We will perform the following checks: 1. Let the end-user visit the app using *.[login to view URL] 2. Check a central table if the sub-domain is registered; if yes, to whom? Then fetch the DB details 3. Connect the end-user/merchnat to their DB 4. Create a super-owner / admin role that can perform CRUD operations for all data owner 5) We need for the the system to be easily updated based on the code and databse