add paged database observer for link preview attachment

Session/Conversations/ConversationViewModel.swift

@@ -265,6 +265,24 @@ public class ConversationViewModel: OWSAudioPlayerDelegate {
                         .allCases
                         .filter { $0 != .wasRead }
                 ),
+                PagedData.ObservedChanges(
+                    table: Attachment.self,
+                    columns: [.state],
+                    joinToPagedType: {
+                        let interaction: TypedTableAlias<Interaction> = TypedTableAlias()
+                        let linkPreview: TypedTableAlias<LinkPreview> = TypedTableAlias()
+                        let linkPreviewAttachment: TypedTableAlias<Attachment> = TypedTableAlias()
+                        
+                        return SQL("""
+                               LEFT JOIN \(LinkPreview.self) ON (
+                                   \(linkPreview[.url]) = \(interaction[.linkPreviewUrl]) AND
+                                   \(Interaction.linkPreviewFilterLiteral())
+                               )
+                               LEFT JOIN \(linkPreviewAttachment) ON \(linkPreviewAttachment[.id]) = \(linkPreview[.attachmentId])
+                            """
+                        )
+                    }()
+                ),
                 PagedData.ObservedChanges(
                     table: Contact.self,
                     columns: [.isTrusted],