WIP: Revamp the session interceptor to work when submission is unset.

[bseeger]

When a session is not null, but does not have a submission id, an error is thrown. This adjusts the session interceptor to successfully catch that scenario and work through it.

This also adds a url parameter to help indicate that a redirect has happened. Then the app can catch that and do something if it wants. Ideally the redirect url could be a configurable parameter, but it doesn't seem like the
interceptor can read the configuration. Must do more testing here.

Issue tracking number 🔗

Description of change ✍️

Priority 🥇

Effect on other applications using FFB 🌊

Testing

✅ Checklist before requesting a review

• Does the new code follow our preferred coding
  style?
• Does the code include javadocs, where necessary?
• Have tests for this feature been added / updated?
• Has the readme been updated?