Ability to "namespace" Context attachments to avoid variable name clashing

We’d like to request the ability to optionally specify a namespace prefix when attaching a Context to a Stack. The goal is to avoid variable collisions when multiple Contexts expose similarly named environment variables (e.g. TF_VAR_vpc_id) and need to be consumed simultaneously by a single Stack.

Example Use Case:

We have separate base infrastructure Contexts for environments like prod and staging, each exporting variables like TF_VAR_vpc_id. Most stacks only need one Context, but occasionally a stack needs to consume both environments. A namespace prefix would allow both to coexist without conflict:

• Attach prod Context with namespace prod → TF_VAR_prod_vpc_id

• Attach staging Context with namespace stage → TF_VAR_stage_vpc_id

This avoids having to namespace all variables in the base Contexts upfront, which would complicate simpler use cases unnecessarily.

Proposed Behaviour:

Support an optional namespace string on Context attachments that is prepended to all exposed variable names (e.g. TF_VAR_{namespace}_{var}).