Create BehaviorOphysSession class

We currently instantiate behavior sessions via BehaviorSession class but instantiate behavior-ophys experiments via BehaviorOphysExperiment class. Since an ophys session can have multiple ophys experiments, it would make sense to create an BehaviorOphysSession class which has a list of BehaviorOphysExperiment.

This would fix an issue which is that ophys_session_id is currently a property of BehaviorOphysExperimentMetadata, when it should be a property of the session, rather than the experiment.

This design is somewhat related to the differences in Mesoscope vs Scientifica (many-to-one vs one-to-one). To take this on, would need to ensure that all tests, and notebooks and Visual Behavior group GLM notebooks would still work.

Before spending a lot of time on this, need to document the planned design, and get it reviewed by team.

Validation criteria:

• BehaviorOphysSession class exists, which has list of BehaviorOphysExperiment
• Can instantiate via ophys_experiment_id (current behavior) or ophys_session_id
• Attributes at the session level should be moved from experiment level to here (one example is ophys_session_id, another is imaging_plane_group_count
• published notebooks have been updated and demonstrate they work
• Visual Behavior representative reports that their critical code still works

Start by reviewing the existing BehaviorSession, BehaviorOphysExperiment, and BehaviorOphysExperimentMetadata entry points, then document the proposed session design for team review. Check how published notebooks and Visual Behavior group GLM notebooks use these classes. Done means the listed validation criteria pass, including both session and experiment instantiation paths and working notebooks.