KIP-240 — AdminClient.listReassignments() AdminClient.describeReassignments()

Discussion Admin

Adds `AdminClient.listReassignments()` and `AdminClient.describeReassignments()` methods (and corresponding protocol) to expose in-progress partition reassignments to admin tooling. Kafka's admin client has no visibility into ongoing partition reassignments, making it impossible to programmatically check current reassignment state before issuing new ones or building tooling that coordinates replica movements.

Details