[AI assisted]: MM-62295: Search and index archived channels as well. (#29796)

We add a new field delete_at in the channels template.

This field is then searched in the SearchChannels function.

Also added tests to verify that archived channels are searched
properly, and also indexed correctly.

https://mattermost.atlassian.net/browse/MM-62295

```release-note
- Now archived channels are searchable with ES/OS if TeamSettings.ExperimentalViewArchivedChannels is enabled.
- If there are old channels which were archived before a bulk index was run, users would need to purge indexes, and do bulk index again. Because those old archived channels are removed from the index when a bulk index is run.
```


Co-authored-by: Mattermost Build <build@mattermost.com>

server/enterprise/elasticsearch/common/indexing_job.go

@@ -408,18 +408,18 @@ func (worker *IndexerWorker) BulkIndexPosts(posts []*model.PostForIndexing, prog
 
 			data, err := json.Marshal(searchPost)
 			if err != nil {
-				worker.logger.Warn("Failed to marshal JSON, skipping this post.", mlog.String("post_id", post.Id))
+				worker.logger.Warn("Failed to marshal JSON, skipping this post.", mlog.String("post_id", post.Id), mlog.Err(err))
 				continue
 			}
 
 			err = worker.addItemToBulkProcessor(indexName, indexOp, searchPost.Id, bytes.NewReader(data))
 			if err != nil {
-				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
+				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 			}
 		} else {
 			err := worker.addItemToBulkProcessor(indexName, deleteOp, post.Id, nil)
 			if err != nil {
-				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
+				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 			}
 		}
 	}
@@ -484,18 +484,18 @@ func (worker *IndexerWorker) BulkIndexFiles(files []*model.FileForIndexing, prog
 
 			data, err := json.Marshal(searchFile)
 			if err != nil {
-				worker.logger.Warn("Failed to marshal JSON")
+				worker.logger.Warn("Failed to marshal JSON", mlog.Err(err))
 				continue
 			}
 
 			err = worker.addItemToBulkProcessor(indexName, indexOp, searchFile.Id, bytes.NewReader(data))
 			if err != nil {
-				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
+				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 			}
 		} else {
 			err := worker.addItemToBulkProcessor(indexName, deleteOp, file.Id, nil)
 			if err != nil {
-				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
+				worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 			}
 		}
 	}
@@ -556,42 +556,35 @@ func BulkIndexChannels(config *model.Config,
 	logger mlog.LoggerIFace,
 	addItemToBulkProcessorFn func(indexName string, indexOp string, docID string, body io.ReadSeeker) error,
 	channels []*model.Channel,
-	progress IndexingProgress) (*model.Channel, *model.AppError) {
+	_ IndexingProgress) (*model.Channel, *model.AppError) {
 	for _, channel := range channels {
 		indexName := *config.ElasticsearchSettings.IndexPrefix + IndexBaseChannels
 
-		if channel.DeleteAt == 0 {
-			var userIDs []string
-			var err error
-			if channel.Type == model.ChannelTypePrivate {
-				userIDs, err = store.Channel().GetAllChannelMemberIdsByChannelId(channel.Id)
-				if err != nil {
-					return nil, model.NewAppError("IndexerWorker.BulkIndexChannels", "ent.elasticsearch.getAllChannelMembers.error", nil, "", http.StatusInternalServerError).Wrap(err)
-				}
-			}
-
-			teamMemberIDs, err := store.Channel().GetTeamMembersForChannel(channel.Id)
+		var userIDs []string
+		var err error
+		if channel.Type == model.ChannelTypePrivate {
+			userIDs, err = store.Channel().GetAllChannelMemberIdsByChannelId(channel.Id)
 			if err != nil {
-				return nil, model.NewAppError("IndexerWorker.BulkIndexChannels", "ent.elasticsearch.getAllTeamMembers.error", nil, "", http.StatusInternalServerError).Wrap(err)
+				return nil, model.NewAppError("IndexerWorker.BulkIndexChannels", "ent.elasticsearch.getAllChannelMembers.error", nil, "", http.StatusInternalServerError).Wrap(err)
 			}
+		}
 
-			searchChannel := ESChannelFromChannel(channel, userIDs, teamMemberIDs)
+		teamMemberIDs, err := store.Channel().GetTeamMembersForChannel(channel.Id)
+		if err != nil {
+			return nil, model.NewAppError("IndexerWorker.BulkIndexChannels", "ent.elasticsearch.getAllTeamMembers.error", nil, "", http.StatusInternalServerError).Wrap(err)
+		}
 
-			data, err := json.Marshal(searchChannel)
-			if err != nil {
-				logger.Warn("Failed to marshal JSON")
-				continue
-			}
+		searchChannel := ESChannelFromChannel(channel, userIDs, teamMemberIDs)
 
-			err = addItemToBulkProcessorFn(indexName, indexOp, searchChannel.Id, bytes.NewReader(data))
-			if err != nil {
-				logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
-			}
-		} else {
-			err := addItemToBulkProcessorFn(indexName, deleteOp, channel.Id, nil)
-			if err != nil {
-				logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
-			}
+		data, err := json.Marshal(searchChannel)
+		if err != nil {
+			logger.Warn("Failed to marshal JSON", mlog.Err(err))
+			continue
+		}
+
+		err = addItemToBulkProcessorFn(indexName, indexOp, searchChannel.Id, bytes.NewReader(data))
+		if err != nil {
+			logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 		}
 	}
 
@@ -653,13 +646,13 @@ func (worker *IndexerWorker) BulkIndexUsers(users []*model.UserForIndexing, prog
 
 		data, err := json.Marshal(searchUser)
 		if err != nil {
-			worker.logger.Warn("Failed to marshal JSON")
+			worker.logger.Warn("Failed to marshal JSON", mlog.Err(err))
 			continue
 		}
 
 		err = worker.addItemToBulkProcessor(indexName, indexOp, searchUser.Id, bytes.NewReader(data))
 		if err != nil {
-			worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName))
+			worker.logger.Warn("Failed to add item to bulk processor", mlog.String("indexName", indexName), mlog.Err(err))
 		}
 	}