Ability to show shards from influx CLI for 2.x

[lesam]

Proposal:

There should be a way to see the shards from a bucket in OSS - possibly a new CLI subcommand

Current behavior:

Internally we maintain a list of shards but there is no way to view it

Desired behavior:

1. Add an optional list of shards to the buckets rest endpoint, it should not be present for cloud but for OSS it can give the list of shards for the bucket.

• see 1.x 'SHOW SHARDS' output - should have at least shard id, start time, end time, and expiry for each shard.

2. Display this information in the CLI (possibly with influx shards list -o myorg --bucket mybucket)

Alternatives considered:

• Add to metrics - metrics aren't very reliable, it feels like this should be in the API

Use case:

• Without visibility into existing shards it can be hard to debug retention policy enforcement.