feat: convert right sidebar notification CTA to frontend plugin

[naincy128]

Description

Scope: New sidebar only (isNewDiscussionSidebarViewEnabled = true). The legacy sidebar is untouched — its behavior is unchanged, and it never reads RIGHT_SIDEBAR_PANELS. No risk of the old sidebar showing or hiding panels differently.

This PR refactors the Learning MFE right sidebar from a single monolithic DiscussionsNotificationsSidebar into two independent, config-driven panels — Discussions and Upsell.

Changes

Sidebar Split

• Deleted combined DiscussionsNotificationsSidebar.tsx and discussions-notifications/index.ts
• Created sidebars/discussions/ — DiscussionsSidebar.tsx, DiscussionsTrigger.tsx (renders only DiscussionsWidget)
• Created sidebars/upsell/ — UpsellSidebar.tsx, UpsellTrigger.tsx (renders only NotificationsWidget / upgrade CTA)
• Renamed DiscussionsNotificationsTrigger.tsx → UpsellTrigger.tsx, extracted discussions-specific logic (topic dispatch, edxProvider check) into DiscussionsTrigger.tsx

Config-Driven Panel Visibility

• Added enabledPanels in SidebarContextProvider.tsx — reads RIGHT_SIDEBAR_PANELS from env.config.js
• Defaults to ['DISCUSSIONS'] — Upsell is disabled by default and opt-in
• Sidebar.tsx checks enabledPanels.includes(sidebarEntry.panelId) before rendering
• SidebarTriggers.tsx filters SIDEBAR_ORDER by enabledPanels before rendering trigger buttons

Sidebar Registry

• Updated sidebars/index.ts: replaced single DISCUSSIONS_NOTIFICATIONS entry with separate DISCUSSIONS and UPSELL entries, each with a panelId for config matching
• Default sidebar changed from DISCUSSIONS_NOTIFICATIONS → DISCUSSIONS

Plugin Slot Updates (in-place, no new slot files)

• NotificationsDiscussionsSidebarSlot: primary ID updated to org.openedx.frontend.learning.right_sidebar.v1, old IDs preserved as idAliases
• NotificationsDiscussionsSidebarTriggerSlot: primary ID updated to org.openedx.frontend.learning.right_sidebar_trigger.v1, old IDs preserved as idAliases
• No new slot files created — Sequence.jsx import unchanged

Constants & i18n

• WIDGETS.NOTIFICATIONS → WIDGETS.UPSELL (deprecated alias NOTIFICATIONS: 'UPSELL' preserved)
• Added rightSidebarTray message, deprecated discussionNotificationTray
• Renamed notificationTitle → upsellTitle (default: "Upgrade")

Config

RIGHT_SIDEBAR_PANELS value	Result
Not set / undefined	Discussions only (default)
['DISCUSSIONS']	Discussions only
['DISCUSSIONS', 'UPSELL']	Both panels
['UPSELL']	Upsell only

Impact

• New sidebar users: Discussions and Upsell are independent panels, configurable via env.config.js
• Old sidebar users: Zero impact — legacy codepath untouched
• Existing plugin consumers: Zero breakage — old slot IDs preserved as idAliases

Ticket

LP-591

[santhosh-apphelix-2u]

It looks like RIGHT_SIDEBAR_PANELS is only used by the new sidebar. The old sidebar still has Notifications and Discussions hard-coded.

Is LP-591 meant to cover only the new sidebar controlled by isNewDiscussionSidebarViewEnabled?

If yes, could we mention that clearly in the PR description? Otherwise, the old sidebar may still show the panel by default.

[santhosh-apphelix-2u]

Why was RightSidebarSlot added if the app still renders NotificationsDiscussionsSidebarSlot?

[naincy128]

I initially added a new RightSidebarSlot, but it wasn't being used because Sequence.jsx still referenced NotificationsDiscussionsSidebarSlot. I updated the existing slot with the new right_sidebar.v1 ID, kept the old IDs as aliases for backward compatibility, and removed the unused RightSidebarSlot file.