MM-24132: Migrate AppError from SaveDirectChannel/channel_store.go (#14318)

* MM-24135: Migrate AppError from SaveChannel/channel_store.go

This is the first POC of migration of store app errors to plain error.

We create a few basic error types in the store package and use
them to return the errors from store methods. In the app layer,
we inspect the error and re-create the exact app errors. This lets
us preserve the same error content, but yet move to plain errors.

Since this is a gradual migration, this means that the error inspection
code will be duplicated across the app layer whenever a store method
is invoked. But all of that should go away once we start propagating
the errors higher up the hierarchy.

There have been a significant amount of changes in the storetest and searchtest
layer, primarily because we have to rename the err variable now that it is of
a different type.

* Addressed review comments

* MM-24132: Migrate AppError from SaveDirectChannel/channel_store.go

This PR migrates 2 new methods SaveDirectChannel and CreateDirectChannel
to return error instead of AppError.

We also need to handle the error internally in SaveMultipleMember for now
until that is migrated too.

* Fix layers

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

app/channel.go

@@ -336,20 +336,44 @@ func (a *App) createDirectChannel(userId string, otherUserId string) (*model.Cha
 	}
 	otherUser := result.Data.(*model.User)
 
-	channel, err := a.Srv().Store.Channel().CreateDirectChannel(user, otherUser)
-	if err != nil {
-		if err.Id == store.CHANNEL_EXISTS_ERROR {
-			return channel, err
+	channel, nErr := a.Srv().Store.Channel().CreateDirectChannel(user, otherUser)
+	if nErr != nil {
+		var invErr *store.ErrInvalidInput
+		var cErr *store.ErrConflict
+		var ltErr *store.ErrLimitExceeded
+		var appErr *model.AppError
+		switch {
+		case errors.As(nErr, &invErr):
+			switch {
+			case invErr.Entity == "Channel" && invErr.Field == "DeleteAt":
+				return nil, model.NewAppError("CreateChannel", "store.sql_channel.save.archived_channel.app_error", nil, "", http.StatusBadRequest)
+			case invErr.Entity == "Channel" && invErr.Field == "Type":
+				return nil, model.NewAppError("CreateChannel", "store.sql_channel.save_direct_channel.not_direct.app_error", nil, "", http.StatusBadRequest)
+			case invErr.Entity == "Channel" && invErr.Field == "Id":
+				return nil, model.NewAppError("SqlChannelStore.Save", "store.sql_channel.save_channel.existing.app_error", nil, "id="+invErr.Value.(string), http.StatusBadRequest)
+			}
+		case errors.As(nErr, &cErr):
+			switch cErr.Resource {
+			case "Channel":
+				return channel, model.NewAppError("CreateChannel", store.CHANNEL_EXISTS_ERROR, nil, cErr.Error(), http.StatusBadRequest)
+			case "ChannelMembers":
+				return nil, model.NewAppError("CreateChannel", "store.sql_channel.save_member.exists.app_error", nil, cErr.Error(), http.StatusBadRequest)
+			}
+		case errors.As(nErr, &ltErr):
+			return nil, model.NewAppError("CreateChannel", "store.sql_channel.save_channel.limit.app_error", nil, ltErr.Error(), http.StatusBadRequest)
+		case errors.As(nErr, &appErr): // in case we haven't converted to plain error.
+			return nil, appErr
+		default: // last fallback in case it doesn't map to an existing app error.
+			return nil, model.NewAppError("CreateDirectChannel", "app.channel.create_direct_channel.internal_error", nil, nErr.Error(), http.StatusInternalServerError)
 		}
-		return nil, err
 	}
 
-	if err = a.Srv().Store.ChannelMemberHistory().LogJoinEvent(userId, channel.Id, model.GetMillis()); err != nil {
+	if err := a.Srv().Store.ChannelMemberHistory().LogJoinEvent(userId, channel.Id, model.GetMillis()); err != nil {
 		mlog.Error("Failed to update ChannelMemberHistory table", mlog.Err(err))
 		return nil, err
 	}
 	if userId != otherUserId {
-		if err = a.Srv().Store.ChannelMemberHistory().LogJoinEvent(otherUserId, channel.Id, model.GetMillis()); err != nil {
+		if err := a.Srv().Store.ChannelMemberHistory().LogJoinEvent(otherUserId, channel.Id, model.GetMillis()); err != nil {
 			mlog.Error("Failed to update ChannelMemberHistory table", mlog.Err(err))
 			return nil, err
 		}