Ensure consistent naming of title fields (#528)

Remove task text and namespace name in migration

Fix lint

Add migration for namespace title

Fix renaming namespace name to title

Rename namespace name field to title

Drop text column at the end of the migration

Add migration for task text to title

Rename task text to title

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/528

pkg/models/task_collection_sort.go

@@ -27,7 +27,7 @@ type (
 
 const (
 	taskPropertyID            string = "id"
-	taskPropertyText          string = "text"
+	taskPropertyTitle         string = "title"
 	taskPropertyDescription   string = "description"
 	taskPropertyDone          string = "done"
 	taskPropertyDoneAtUnix    string = "done_at_unix"