🐛 Fix default unique_extra_keys value

The current default value of `None` for the `unique_extra_keys` in the
`BaseSubmissionController` is not a valid approach for setting the default.
For `BaseSubmissionController`s, the user should still specify the unique extra keys,
since they can't be derived from a parent node. For the
`FromGroupSubmissionController`, it is sensible to use the `_aiida_hash` as a default
value, instead of `None`.

aiida_submission_controller/base.py

@@ -3,7 +3,6 @@
 import abc
 import logging
 import time
-from typing import Optional
 
 from aiida import engine, orm
 from aiida.common import NotExistent
@@ -54,7 +53,7 @@ class BaseSubmissionController(BaseModel):
     """Label of the group to store the process nodes in."""
     max_concurrent: int
     """Maximum concurrent active processes."""
-    unique_extra_keys: Optional[tuple] = None
+    unique_extra_keys: tuple
     """Tuple of keys defined in the extras that uniquely define each process to be run."""
 
     _validate_group_exists = field_validator("group_label")(validate_group_exists)

aiida_submission_controller/from_group.py

@@ -15,6 +15,8 @@ class FromGroupSubmissionController(BaseSubmissionController):  # pylint: disabl
     and define the abstract methods.
     """
 
+    unique_extra_keys: Optional[tuple] = ("_aiida_hash",)
+    """Tuple of keys defined in the extras that uniquely define each process to be run."""
     parent_group_label: str
     """Label of the parent group from which to construct the process inputs."""
     filters: Optional[dict] = None