observeIsAppMember
open suspend override fun observeIsAppMember(appId: QualifiedIDEntity, conversationId: ConversationIDEntity): <Error class: unknown class><QualifiedIDEntity?>
Returns the userId only if the given user is a member of the conversation.
NOTE: This may look redundant since it returns the same userId that is passed in. However, this follows the existing patter used for legacy bots/services, where a serviceId is resolved to a userId via Member table.
We keep this behavior for consistency while old bots/services and new Apps coexist. Effectively, this acts as a member check + userId passthrough.
Can be refactored to a boolean check (isMember) in the future once old bots/services dependencies are removed.