Use JSON response for "user/logout" (#25522)

The request sent to "user/logout" is from "link-action", it expects to
get JSON response.

routers/web/auth/auth.go

@@ -383,7 +383,7 @@ func SignOut(ctx *context.Context) {
 		})
 	}
 	HandleSignOut(ctx)
-	ctx.Redirect(setting.AppSubURL + "/")
+	ctx.JSONRedirect(setting.AppSubURL + "/")
 }
 
 // SignUp render the register page

templates/base/head_navbar.tmpl

@@ -68,7 +68,7 @@
 					</div>
 
 					<div class="divider"></div>
-					<a class="item link-action" href data-url="{{AppSubUrl}}/user/logout" data-redirect="{{AppSubUrl}}/">
+					<a class="item link-action" href data-url="{{AppSubUrl}}/user/logout">
 						{{svg "octicon-sign-out"}}
 						{{.locale.Tr "sign_out"}}
 					</a>
@@ -186,7 +186,7 @@
 					{{end}}
 
 					<div class="divider"></div>
-					<a class="item link-action" href data-url="{{AppSubUrl}}/user/logout" data-redirect="{{AppSubUrl}}/">
+					<a class="item link-action" href data-url="{{AppSubUrl}}/user/logout">
 						{{svg "octicon-sign-out"}}
 						{{.locale.Tr "sign_out"}}
 					</a>

tests/integration/signout_test.go

@@ -16,7 +16,7 @@ func TestSignOut(t *testing.T) {
 	session := loginUser(t, "user2")
 
 	req := NewRequest(t, "POST", "/user/logout")
-	session.MakeRequest(t, req, http.StatusSeeOther)
+	session.MakeRequest(t, req, http.StatusOK)
 
 	// try to view a private repo, should fail
 	req = NewRequest(t, "GET", "/user2/repo2")