[Feature]: Generic per-participant/person user-settings store persisted via the SDK (shared across IME and Web)

[rdevoogtatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the COMET-SDK
• I have searched open and closed issues to ensure it has not already been reported

Description

Neither the IME nor the Web app can persist per-user UI settings server-side. The IME writes a local per-user JSON file (PluginSettingsService), and the Web app has no durable per-user store (but could be done with local browser storage). Both approaches are per-device, lost on profile/cache clear, and can't be shared between tools.

We would like a generic, SDK-provided mechanism to persist arbitrary per-user settings in the database, keyed to the Participant (or Person), so any client can read/write namespaced settings and have them travel with the user across devices and tools.

Proposal

• Expose a per-user settings container through the SDK/DAL (e.g. a JSON/string blob keyed by owner + a client-defined namespace such as relationshipmatrix.savedConfigurations).
• Provide a read/write API on the SDK (analogous to how other Things are read/updated), respecting existing permission and revision handling.
• Keep it schema-agnostic so each tool/plugin owns the shape of its own settings.

Acceptance criteria

• A client can store and retrieve a namespaced settings value for the current participant via the SDK.
• Settings persist server-side and survive reconnects / other devices.
• Permissions: a participant can read/write only their own settings.
• Both the IME and the Web app can consume the same API.

Notes / open questions

• Data model: extend an existing type vs. a new dedicated construct; storage format (JSON string).
• Visibility / permissions and whether settings live per-model or globally per-user.
• Migration path; whether the IME migrates its local plugin settings onto this store.
• First consumer: migrate the Relationship Matrix saved configurations (COMET-WEB) onto the new store.

Context

Split out of the CDP4-COMET-WEB Relationship Matrix work (STARIONGROUP/COMET-WEB-Community-Edition#821). The Web app currently has no saved-configuration persistence pending this SDK capability.

• COMET version:
  • CDP4Common:
  • CDP4JsonSerializer:
  • CDP4Dal:
  • CDP4JsonFileDal:
  • CDP4ServicesDal:
  • CDP4WspDal:
  • Other:
• Environment (Operating system, version and so on):
• .NET Framework version:
• Additional information: