【解決方法】異なるデータベースで REST API を使用する

I have a data system created with MS Sql Server. The system works with 28 tables. We create a customer-specific database containing the same tables for each customer to whom we sell the product. and there is a separate database where we store customer information. But at the same time, we open a port for each client and start a service. This is not useful for us with the increasing number of customers. I just want to publish a service and add config to the service for client database information in IIS and direct the api to the relevant database with a parameter or header parameter added to the url requests (obviously I have no idea how). Can you help on how to do this?<pre>

What I have tried:

<pre>Unfortunately I haven't been able to try anything. because i don't know about service start.