Shared modules living in a submodule

The submodule is a directory tree of module directories, not a build of its own. It has no settings file and no root build script — the parent build's settings file is the only thing that turns those directories into Gradle projects.

# .gitmodules
[submodule "<shared>"]
    path = <shared>
    url = https://<host>/<org>/<shared>

// settings.gradle.kts — adapted
val sharedDir  = File(rootDir, "<shared>")          // the submodule's checkout root
val serviceDir = File(rootDir, "<shared>/service")

include(":common", ":data", ":domain", ":<service-a>")