[Feature Request]: allow environmental variable control checkbox "Use HTML format in mail body" in "Mail" transform

[gmitter-ef]

What would you like to happen?

What would you like to happen?

Follow-up of https://github.com/apache/hop/issues/5628.

For "Mail transform" we would like to be able to control the "Use HTML format in mail body" checkbox via an environmental variable:

Documentation would include valid values for this variable, and the logic that is applied when the variable is empty/unset, or contains invalid values. Similary, what would happen when the checkbox conflicts with the value of the variable. Optimally, the checkbox would be greyed out when the config variable is used?

Issue Priority

Priority: 3

Issue Component

Component: Hop Gui, Component: Transforms