feat: Add Sign-out functionality (#46)

#37 implemented the Sign-_in_ flow, but there wasn't a Sign-_out_ flow as part of that PR (aside from letting the cookie expire... or manually deleting the cookie...), which is obviously not ideal.

This PR implements a basic sign-out flow, along with a very simple user dropdown:
![2022-01-21 18 09 14](https://user-images.githubusercontent.com/88213859/150620847-94e4d22f-1dcf-451e-8b4a-cec24702ea6c.gif)

Bringing in a few pruned down components for the `<UserDropdown />` to integrate into the `<NavBar />`.

In addition, this also implements a simple back-end API for `/logout` which just clears the session token.

coderd/coderd.go

@@ -35,6 +35,7 @@ func New(options *Options) http.Handler {
 			})
 		})
 		r.Post("/login", users.loginWithPassword)
+		r.Post("/logout", users.logout)
 		r.Route("/users", func(r chi.Router) {
 			r.Post("/", users.createInitialUser)
 

coderd/users.go

@@ -237,6 +237,20 @@ func (users *users) loginWithPassword(rw http.ResponseWriter, r *http.Request) {
 	})
 }
 
+// Clear the user's session cookie
+func (*users) logout(rw http.ResponseWriter, r *http.Request) {
+	// Get a blank token cookie
+	cookie := &http.Cookie{
+		// MaxAge < 0 means to delete the cookie now
+		MaxAge: -1,
+		Name:   httpmw.AuthCookie,
+		Path:   "/",
+	}
+
+	http.SetCookie(rw, cookie)
+	render.Status(r, http.StatusOK)
+}
+
 // Generates a new ID and secret for an API key.
 func generateAPIKeyIDSecret() (id string, secret string, err error) {
 	// Length of an API Key ID.

coderd/users_test.go

@@ -2,12 +2,14 @@ package coderd_test
 
 import (
 	"context"
+	"net/http"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/coder/coder/coderd"
 	"github.com/coder/coder/coderd/coderdtest"
+	"github.com/coder/coder/httpmw"
 )
 
 func TestUsers(t *testing.T) {
@@ -75,3 +77,30 @@ func TestUsers(t *testing.T) {
 		require.Len(t, orgs, 1)
 	})
 }
+
+func TestLogout(t *testing.T) {
+	t.Parallel()
+
+	t.Run("LogoutShouldClearCookie", func(t *testing.T) {
+		t.Parallel()
+
+		server := coderdtest.New(t)
+		fullURL, err := server.URL.Parse("/api/v2/logout")
+		require.NoError(t, err, "Server URL should parse successfully")
+
+		req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, fullURL.String(), nil)
+		require.NoError(t, err, "/logout request construction should succeed")
+
+		httpClient := &http.Client{}
+
+		response, err := httpClient.Do(req)
+		require.NoError(t, err, "/logout request should succeed")
+		response.Body.Close()
+
+		cookies := response.Cookies()
+		require.Len(t, cookies, 1, "Exactly one cookie should be returned")
+
+		require.Equal(t, cookies[0].Name, httpmw.AuthCookie, "Cookie should be the auth cookie")
+		require.Equal(t, cookies[0].MaxAge, -1, "Cookie should be set to delete")
+	})
+}