MM-24133: Migrate AppError from bot_store.go (#14339)

* 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.

* MM-24133: Migrate AppError from bot_store.go

* Fix errors

* Fix err

* Fix bad return

* Fix vet errors

* Fix incorrect error check

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

cmd/mattermost/commands/user.go

@@ -529,9 +529,9 @@ func botToUser(command *cobra.Command, args []string, a *app.App) error {
 		}
 	}
 
-	appErr = a.Srv().Store.Bot().PermanentDelete(user.Id)
-	if appErr != nil {
-		return fmt.Errorf("Unable to delete bot. Error: %s", appErr.Error())
+	err = a.Srv().Store.Bot().PermanentDelete(user.Id)
+	if err != nil {
+		return fmt.Errorf("Unable to delete bot. Error: %v", err)
 	}
 
 	CommandPrettyPrintln("id: " + user.Id)

cmd/mattermost/commands/user_test.go

@@ -126,14 +126,14 @@ func TestDeleteUserBotUser(t *testing.T) {
 	user, err := th.App.Srv().Store.User().Save(model.UserFromBot(bot))
 	require.Nil(t, err)
 	bot.UserId = user.Id
-	bot, err = th.App.Srv().Store.Bot().Save(bot)
-	require.Nil(t, err)
+	bot, nErr := th.App.Srv().Store.Bot().Save(bot)
+	require.Nil(t, nErr)
 
 	th.CheckCommand(t, "user", "delete", bot.Username, "--confirm")
 	_, err = th.App.Srv().Store.User().Get(user.Id)
 	require.Error(t, err)
-	_, err = th.App.Srv().Store.Bot().Get(user.Id, true)
-	require.Error(t, err)
+	_, nErr = th.App.Srv().Store.Bot().Get(user.Id, true)
+	require.Error(t, nErr)
 }
 
 func TestConvertUser(t *testing.T) {