I don't see how writing "one more OAuth client" or "one more login thing" using Spring Boot is not reinventing the wheel in itself.
If you really care about "not reinventing the wheel" there are ready-made paid solutions such as Auth0 and Cognito, plus self-hostable open-source options like Keycloak, Authelia, and Dex.
Also, Spring Boot itself uses third-party libraries for OAuth and Authentication, like Ninbus, which people can drop-in in their non-Spring Java apps.
If you really care about "not reinventing the wheel" there are ready-made paid solutions such as Auth0 and Cognito, plus self-hostable open-source options like Keycloak, Authelia, and Dex.
Also, Spring Boot itself uses third-party libraries for OAuth and Authentication, like Ninbus, which people can drop-in in their non-Spring Java apps.