Enhance transform to support list of source indices

[doomma]

Is your feature request related to a problem? Please describe.
Current transform api is limiting with the lack of support for providing a list of source indices to transform from
Describe the solution you'd like
Add support to provide an array of indices (for example, ["my-index-000001", "my-index-000002"]), or an array of index patterns (for example, ["my-index-", "my-other-index-"]

Describe alternatives you've considered
Name indices in a pattern and provide a wild card. But this does not scale well

Additional context
Add any other context or screenshots about the feature request here.