Move source code to /spring-boot-starter/starter-client while preserving commit history
Add license headers
GroupIds & ArtifactIds are compliant with other spring-boot modules
Spring Boot: org.camunda.bpm.springboot:camunda-bpm-spring-boot-starter-external-task-client
I put the bpm in the artifact name even though it is considered as a legacy term to make it consistent with the other artifacts; I think consistency is more important here
Sub-task
L3 - Default