When adding a new task relation, the task search input would previously show all tasks in a seemingly random order, including done tasks. Usually, you don't care about these done tasks when adding relations. This change modifies the sort order so that done tasks show up last in the search results.
Username and password are validated in the api for length and whitespaces. Previously, the api would tell the user "hey you got it wrong" but the error was not reflected properly in the UI. This change implements a client-side validation which mirrors the one from the api, allowing instant validation and better error UX.
