Add OpenFGA Service Connection

[rwinch]

It would be nice to add OpenFGA Service Connection which will automatically map the OpenFGA Docker Container to the Spring Boot environment. An example can be found in the fga-spring-example.

[eddumelendez]

I'm working on this and will be submitting smalls PRs in order to achieve it.

This is my proposal

• Use @AutoConfiguration. See Use AutoConfiguration annotation instead #64
• Update example to use Testcontainers OpenFGA module Add Testcontainers Service Connection in examples #63
• Support Gradle multi-project for upcoming openfga-spring-boot-testcontainers and openfga-spring-boot-docker-compose modules. Move existing src folder to openfga-spring-boot-starter. See chore: move src folder to subproject #69
• Add Service Connection from Testcontainers (openfga-spring-boot-testcontainers)
• Add Service Connection from Docker Compose (openfga-spring-boot-docker-compose)
• Update example to use @ServiceConnection

WDYT @jimmyjames ?