Moving a subtask with its parent does not validate the custom field context

Summary:

When moving a parent issue, if it has subtasks with custom field values that have different contexts in the source and target project, they will not be validated.

Steps to Reproduce:

1. Create Custom Field with different contexts for Project A & Project B (as in the attached screenshot).
2. Create Issue in Project A with one value in the Custom Field (e.g.: create it in Llama with option D).
3. Create a sub-task of that issue with the same value for the custom field.
4. Move the parent issue to Project B (e.g.: Goose).

Expected Results:

The custom field context validation is applied to the subtask and will not be allowed to move it as a value of D (as this does not exist within the context for the target project).

Actual Results:

The subtask is moved with the same value in the custom field, so it is using the context of the previous project (e.g.: Llama).