Sitcom star-turned-auteur? It doesn’t seem very likely, does it? It’s doubtful even Ron Howard aspires to the role. But just on the strength of his first film, Josh Radnor seems destined to confound expectations. The star of “How I Met Your Mother” spent years pursuing financing for his debut, which he wrote during the first seasons of the show. His cast, not huge stars but still recognizable names, worked for scale. This independent film was clearly a labor of love. Don’t mistake it for a vanity project by a young actor who is desperate to be taken more seriously, though. “Happythankyoumoreplease” is a film that embraces all of our complicated humanity.