Multi-domaine spring-boot application (or multi-tenant)

Hello everyone
I want to develop a multi-domain application.
I just want to lay the foundations of architecture.
my application must be able to know who is connecting from the domain.
Let me explain: if someone connects from Germany, the application is able to route the person to the correct database.
look at the schema everything is explained.
if you have any questions please tell me.
The framworks that are chosen are:
spring-boot v2
spring-data-jpa
spring-data-rest
sping-mvc (thymeleaf for test) angular later
mysql with 3 schemas (city1, city2 and city3 each one with two tables (users and roles)
Regards