Implementing Open API client for JVM based languages

**Description**

Similar to [airflow-client-python](https://github.com/apache/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](https://github.com/apache/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

Start by reviewing the existing airflow-client-python project and the OpenAPI specifications, then examine the airflow-client-java repository referenced in the issue. Define the scope for a stable JVM client covering Java, Scala, and Kotlin use cases; done means the client is generated or maintained there and supports seamless import and usage.

Written by the indexing model from the issue text.