[BUG] Transforms - all data shows "-" when field is inside an object

[triggerhappy17]

Describe the bug

When you have your data fields in objects, ie:
obj.field1
obj.field2
....

all columns show as "-" and so you cannot create any transform, agg etc. Fields that are not part of objects are ok.

To Reproduce
Steps to reproduce the behavior:

1. create a index template that as a object. inside that object add some fields.
2. insert data
3. try and complete a transform -> transform job->create transform job. Point at your source index. Create a new destination index, next ... all coums show "-".
4. See error

Expected behavior
transforms should support fields within objects.

OpenSearch Version
2.16

Dashboards Version
2.16

Plugins

opensearch deafault container