Feature: Add 8x8 CPaaS SMS and WhatsApp providers

Feature description

Add 8x8 CPaaS as a Novu delivery provider across two channels:

• 8x8 SMS — single SMS with global delivery, optional alphanumeric/numeric Sender ID, and REJECTED-status handling (8x8 SMS API).
• 8x8 WhatsApp Business — freeform text plus template, interactive, and media message types via provider overrides (8x8 Messaging Apps / ChatApps API).

Both are send-only notification channels (not conversational/agent channels), so this is a focused provider addition with no changes to the agents / conversation-runtime surface.

Why is this feature needed?

8x8 CPaaS is a widely used communications platform (SMS, Chat Apps, Voice, Video). Teams already on 8x8 for their messaging currently can't use it as a Novu provider and have to fall back to a generic webhook or a second vendor. First-class 8x8 SMS + WhatsApp support lets those teams route Novu notifications through their existing 8x8 sub-accounts and Sender IDs.

✌️ How do you aim to achieve this?

Already implemented and opened as a PR: #12200 (rebased on latest next, MERGEABLE, 10/10 unit tests, verified end-to-end against a live 8x8 account).

It follows the same provider-registration pattern as the recently merged #12411 (Photon iMessage): provider classes + specs under packages/providers, SmsProviderIdEnum / ChatProviderIdEnum entries, credential + channel metadata, provider-override registry, framework chat schema, DAL credential key (subAccountId), SMS/chat factories + handlers with phone-endpoint routing, and dashboard branding/icons.

This issue is the proposal that the contributing guide asks for before implementation, filed to give the existing PR a home in triage.

️ Additional Information

• Implementation PR: #12200
• Precedent (same integration surface, merged Sep 14): #12411
• Provider docs followed: https://docs.novu.co/community/add-a-new-provider