In https://docs.gradle.org/current/dsl/org.gradle.api.artifacts.dsl.DependencyHandler.html you can find description of two notations for external dependency. There is also information, that:
In both notations, all properties, except name, are optional.
When and how can I use external dependency without group? Can you give me existing examples?
btw, shouldn’t be
group: group instead of
group: group: in:
configurationName group: group:, name: name, version: version, classifier: classifier, ext: extension