Implementing Open API client for JVM based languages

[pateash]

Description

Similar to airflow-client-python,
we should have a client for JVM based languages (Java/Scala/Kotlin)

We will generate and maintain a stable version of Api Client in a repository
airflow-client-java

Although, using OpenAPI Specs user is able to generate API Client themselves,
but there might be some issues that needed to be fixed, which the community will be able to fix and provide users the seamless import and usage of clients.

Are you willing to submit a PR?
YES

[pateash]

@potiuk as discussed in the mail chain, creating this Issue.

There is a lot of discussion and work is happening around Airflow OpenAPI spec and clients,
All suggestions and concerns are welcome.