Default user prefix to user name

[samuelbray32]

spyglass/src/spyglass/utils/dj_mixin.py

Line 200 in 6122f07

user_prefix = dj.config.get("custom", dict()).get("database.prefix")

Could we allow a default of user_name for the user_prefix value here? This would match the behavior in the custom_nwbfile file here and reduce setup for users migrating to the custom analysis nwbfile tables