* support finding segments from a AWS S3 storage.
* add more Uts
* address comments and add a document for the feature.
* update docs indentation
* update docs indentation
* address comments.
1. add a Ut for json ser/deser for the config object.
2. more informant error message in a Ut.
* address comments.
1. use @Min to validate the configuration object
2. change updateDescriptor to a string as it does not take an argument otherwise
* fix a Ut failure - delete a Ut for testing default max length.
`insert-segment-to-db` is a tool that can insert segments into Druid metadata storage. It is intended to be used
to update the segment table in metadata storage after people manually migrate segments from one place to another.
It can also be used to insert missing segment into Druid, or even recover metadata storage by telling it where the
segments are stored.
Note: This tool expects users to have Druid cluster running in a "safe" mode, where there are no active tasks to interfere
the segments being inserted. Users can optionally bring down the cluster to make 100% sure nothing is interfering.