Feature: Preferences

1. Overview

• Goal: Preferences are the small set of personal settings that shape how Registry looks and behaves for one signed-in user: the theme, the interface language, and the active project profile — the event the user is currently "inside". Because preferences are stored server-side, they follow the user to any device: sign in elsewhere and the same theme, language and active event are already applied.
• Who uses it: Every signed-in user, over their own preferences only. There is no cross-user administration here.
• Option required: None. This is a global, per-user feature, governed by global roles rather than project options.

2. Roles & Permissions

This is a global, per-user feature: it uses the platform-wide roles USER_ADMINISTRATOR and USER. Both have identical rights here — each acting only on their own preferences. See Roles & Permissions for the full model, and Domain Model → User for where preferences live.

Role	Permitted actions	Conditions / Scope
USER (global, default)	R U (own)	May read and update their own theme, language and active profile. No special permission needed — authenticated is enough.
USER_ADMINISTRATOR (global)	R U (own)	Identical rights, and only over their own preferences. Being a platform administrator grants no access to another user's preferences.

3. Business rules

• Per-user and server-side. Preferences belong to one user and are stored on the server, so they follow the user to any device rather than living in a single browser.
• Theme. One of SYSTEM, LIGHT or DARK (see Domain Model → Theme). SYSTEM follows the device's own light/dark setting.
• Language. English (en) or French (fr). Switching language re-localizes the interface labels immediately.
• Active project profile. Selecting an active profile switches which event the user is "inside" and resets the in-app project context to that event. The profile can be chosen directly by its id, or by naming a project (the user's profile on that project is selected).
• Own scope only. Every operation acts on the caller's own preferences; there is no endpoint to read or change someone else's.

4. Behavioral scenarios (BDD)

Scenario: A user switches to dark theme
  Given I am a signed-in user
  When I set my theme to DARK
  Then my preference is saved server-side
  And the interface renders in dark mode on every device I sign in from

Scenario: The system theme follows the device
  Given I am a signed-in user
  When I set my theme to SYSTEM
  Then the interface follows my device's own light/dark setting

Scenario: A user switches the interface language
  Given I am a signed-in user with the interface in English
  When I set my language to fr
  Then the interface labels are re-localized to French
  And the preference is saved server-side

Scenario: Selecting an active profile switches the current event
  Given I am a signed-in user with accepted profiles on project A and project B
  And project A is my active profile
  When I select my profile on project B as active
  Then project B becomes the event I am "inside"
  And the in-app project context is reset to project B

Scenario: Selecting an active profile by project
  Given I am a signed-in user with an accepted profile on project B
  When I select the active profile by naming project B
  Then my profile on project B becomes active

Scenario: Preferences follow the user to another device
  Given I set my theme to DARK and my language to fr on one device
  When I sign in from a different device
  Then the interface is already in dark mode and French

Scenario: An administrator cannot change another user's preferences
  Given I am a global USER_ADMINISTRATOR
  When I attempt to change another user's theme
  Then there is no such capability — preferences act only on the caller's own account

5. API surface

REST endpoints backing this feature, under /api/v2/users/preferences. Every call is authenticated and acts on the caller's own preferences; there are no permissions beyond being signed in. See Technical → API Reference.

Method	Path	Purpose	Permission
POST	/users/preferences/theme	Set the theme (SYSTEM / LIGHT / DARK)	Authenticated (self)
POST	/users/preferences/language	Set the interface language (en / fr)	Authenticated (self)
POST	/users/preferences/select-profile	Select the active profile (body: profileId or projectId)	Authenticated (self)