Persist user answers on Continue

[Andrew-Folga]

Integrate backend persistence for application answers via StatePersistenceService

Description:

This PR introduces StatePersistenceService, which handles saving and retrieving users’ application answers. Application state is now persisted to grants-ui-backend (MongoDB) whenever users click Continue, ensuring progress is not lost between sessions.

Changes:

• Added StatePersistenceService to manage state lifecycle.
• Removed the legacy “Save and Return” button from the UI.
• Deprecated use of Redis for GrantsUI state management.
• Updated helpers and services to support backend-driven persistence.

Acceptance Criteria:

• When a user answers one or more questions and selects Continue, their responses are persisted in MongoDB.
• Previously saved answers are automatically reloaded when a user returns to their application.

Notes:

• MongoDB (via grants-ui-backend) is now the single source of truth for application state.
• Frontend no longer depends on Redis for state management.

Testing:

• Verified persistence to MongoDB occurs on Continue.
• Confirmed previously answered questions load correctly when revisiting.
• Validated removal of the “Save and Return” button.

[alanplatt]

Looks good, my only issue it that we should look to set the ttl to not expire if we're going to handle this in the backend so we're not doing it in two places.

[Andrew-Folga]

Actually I managed to remove stored and ttl alltogether as not needed.

[alanplatt]

Why call clearState at all now from the confirmation controller?

[Andrew-Folga]

Hey @alanplatt re calling clearState in confirmation controller - do we want to remove it or rather keep it in for the follow up story to mark/flag the application as submitted; btw the story talks nothing about submission hmm

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
97.0% Coverage on New Code
0.0% Duplication on New Code

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