[7.2][DOCS] Adds more validation details for data frame transforms (#44714) (#44727)

Author: lcawl

docs/reference/data-frames/apis/put-transform.asciidoc

@@ -40,6 +40,11 @@ structure (known as a {dataframe}). The ID for each document in the
 per entity. For more information, see
 {stack-ov}/ml-dataframes.html[{dataframe-transforms-cap}].
 
+When the {dataframe-transform} is created, a series of validations occur to
+ensure its success. For example, there is a check for the existence of the
+source indices and a check that the destination index is not part of the source
+index pattern.
+
 IMPORTANT:  You must use {kib} or this API to create a {dataframe-transform}.
             Do not put a {dataframe-transform} directly into any
             `.data-frame-internal*` indices using the Elasticsearch index API.

docs/reference/data-frames/apis/start-transform.asciidoc

@@ -41,6 +41,13 @@ aggregations, the transform uses dynamic mappings unless a template exists or
 the destination index already exists. Mapping definitions in the destination
 index take precedence over dynamic mappings and templates.
 
+When a {dataframe-transform} starts, a series of validations occur to ensure its
+success. However, there are no initial privilege checks. When {es}
+{security-features} are enabled, the {dataframe-transform} remembers which roles
+the user that created it had at the time of creation and uses those same roles.
+If those roles do not have the required privileges on the source and destination
+indices, the {dataframe-transform} fails when it attempts unauthorized operations.
+
 [[start-data-frame-transform-path-parms]]
 ==== {api-path-parms-title}