[Feature Request]: Support Variable Substitution for Default Value in Stream Lookup

[dsanderbi]

What would you like to happen?

I would like to request a feature enhancement for the Stream Lookup transform.
Currently, the transform provides an option to define a default value when no match is found during the lookup process.

However, at the moment, the default value must be hardcoded,
which limits the flexibility of the transformation.
It would be highly beneficial if the default value field supported variable substitution,
allowing users to reference environment variables or parameters (e.g., ${DEFAULT_LOOKUP_VALUE}) instead of hardcoding static values.

Issue Priority

Priority: 2

Issue Component

Component: Transforms

[mattcasters]

It's a great idea. Do we need to add an explicit option for this to remain compatible with previous releases?
In other words, are we worried about people setting ${SOMETHING} as a default value in combination with the SOMETHING variable containing an actual value? I would think that the chance is very low but not zero.
Perhaps adding a note in the documentation can suffice.