[FLINK-27322] Add license headers and spotless checks for them

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.14.4
• Fix Version/s: 1.15.0
• Component/s: Documentation / Training / Exercises
• Labels: pull-request-available
• Assignee: Nico Kruber
• Reporter: Nico Kruber
• Created: 20/Apr/22 10:21
• Updated: 21/Apr/22 10:35
• Resolved: 21/Apr/22 10:35

Description

It looks as if there are a couple of files that are missing their appropriate license headers, e.g. https://github.com/apache/flink-training/blob/0b1c83b16065484200564402bef2ca10ef19cb30/common/src/main/java/org/apache/flink/training/exercises/common/datatypes/RideAndFare.java

We should fix that by:

1. adding the missing license headers
2. adding spotless checks to ensure this doesn't happen again

Potential downside: if a user doing the training exercises creates files on their own, these would need the license header as well. On the other hand, a simple `./gradlew spotlessApply` can fix that easily

Issue Links

• links to: GitHub Pull Request #47