appview: basic logout functionality

This should be in the profile dropdown.

appview/auth/auth.go

···
 	return s.Status
 }
 
+func (a *Auth) ClearSession(r *http.Request, w http.ResponseWriter) error {
+	clientSession, _ := a.Store.Get(r, appview.SessionName)
+	clientSession.Options.MaxAge = -1
+	return clientSession.Save(r, w)
+}
+
 func (a *Auth) StoreSession(r *http.Request, w http.ResponseWriter, atSessionish Sessionish, pdsEndpoint string) error {
 	clientSession, _ := a.Store.Get(r, appview.SessionName)
 	clientSession.Values[appview.SessionHandle] = atSessionish.GetHandle()

appview/pages/templates/layouts/topbar.html

···
 {{ define "layouts/topbar" }}
     {{ with .LoggedInUser }}
-        <nav class="flex items-center justify-center space-x-4 mb-4 py-2 border-b border-l border-r border-black">
+        <nav
+            class="flex items-center justify-center space-x-4 mb-4 py-2 border-b border-l border-r border-black"
+        >
             <a
                 href="/"
                 hx-boost="true"
···
                     >my profile</a
                 >
             {{ end }}
+            <button hx-get="/logout" class="btn">logout</a>
         </nav>
     {{ else }}
         <a href="/login" class="btn my-2 no-underline">login</a>

appview/state/state.go

···
 	}
 }
 
+func (s *State) Logout(w http.ResponseWriter, r *http.Request) {
+	s.auth.ClearSession(r, w)
+	s.pages.HxRedirect(w, "/")
+}
+
 func (s *State) Timeline(w http.ResponseWriter, r *http.Request) {
 	user := s.auth.GetUser(r)
 	s.pages.Timeline(w, pages.TimelineParams{
···
 	r.Handle("/static/*", s.pages.Static())
 
 	r.Get("/", s.Timeline)
+
+	r.Get("/logout", s.Logout)
 
 	r.Get("/login", s.Login)
 	r.Post("/login", s.Login)