add prefix option to DataTransformMDB class

[DylanWelzel]

This pull request improves the handling of identifier prefixes in the DataTransformMDB class by allowing prefixes to be defined at the node level in the transformation graph and ensuring they are automatically applied during data transformation. The changes centralize and standardize how prefixes are managed, making the codebase more robust and easier to configure.

Prefix handling enhancements:

• Added support for defining identifier prefixes as node attributes in the graph, with automatic prefix application when converting identifiers to nodes.
• Introduced the _apply_prefix method to encapsulate prefix logic, ensuring identifiers are correctly formatted with their configured prefixes.

Integration of prefix logic in data transformation:

• Updated the _copy method to use _apply_prefix, applying prefixes to _id fields when copying identifiers.
• Modified the _build_hit_miss_lsts function to apply prefixes to _id fields when constructing new documents, using the new _apply_prefix method.
• Updated the call to _copy in key_lookup_batch to pass the output type, enabling correct prefix application during batch lookups.