Fix/external id notification

[IfDougelseSa]

Description

Fixes plugin notifications for SSO-authenticated users by querying the SSO provider's external_id instead of using the notification plugin's name.

Problem

Plugin notifications were failing for users authenticated via SSO (GitHub OAuth, Google, SAML, etc.) because the code was looking up external_id using the notification plugin's name instead of the SSO authentication provider.

Example:

• User logs in via provider = "github" (SSO)
• Code searches for provider = "discord" (notification plugin)
• No match found → ReceiverExternalID is empty

Solution

Query all external logins for the user and use the most recent one (ORDER BY updated_at DESC).

Changes

• Add ORDER BY updated_at DESC to GetUserExternalLoginList
• Update notification code to query all external logins
• Use first login from ordered list (most recent)

Testing

Before:
Receiver External ID: ← Empty

After:
Receiver External ID: 81540136 ← Populated

Tested with GitHub OAuth SSO and test notification plugin.