Batch update users (chat API) (v2, tenant actor)

Auth: Tenant Actor

Same operation as /v2/chats/users but with the target app explicit in the path. This is the preferred route for backend / tenant-admin integrations, especially when:

• You're acting on a CHILD app from a parent-app B2B token. The legacy /v2/chats/users route uses reqUser.appId for the xmppUsername-prefix check and DB scope, so a parent-app token can never satisfy xmppUsername.startsWith(<childAppId>_) for a child app's user. This route uses the path :appId instead.

• You want the target appId to be unambiguous in the URL for ops/audit/logging purposes (matches /v2/apps/{appId}/chats/broadcast and the rest of the path-explicit tenant-actor surface).

Auth model:

• B2B Server JWT: allowed when :appId is the token's own app or one of its child apps (parentAppId equality).
• User JWT: allowed when the caller has an appUsers.update Acl on :appId.

Request body shape and response envelope are identical to /v2/chats/users (same Joi schema, same patchChatUsersBatchService under the hood; only the auth + the appId resolution differ).