bumped to 1.2.1 (opensearch-project#266)

Signed-off-by: Amit Galitzky <amgalitz@amazon.com>

Add 1.2 release notes (opensearch-project#256)

Signed-off-by: Ankit Kala <ankikala@amazon.com>

Handle case when leader index mapping is not available

In case of large documents, leader mapping is not immediately available which causes
an NPE and fails the shard task. Checking whether mapping is available and throwing
exception if it not available so that the call can be retried.

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

Handle case when leader index mapping is not available

In case of large documents, leader mapping is not immediately available which causes
an NPE and fails the shard task. Checking whether mapping is available and throwing
exception if it not available so that the call can be retried.

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

Initial commit