Add go back link to auth error

Author: LEDfan

src/main/java/eu/openanalytics/containerproxy/ui/AuthController.java

@@ -80,6 +80,7 @@ public Object getLoginPage(@RequestParam Optional<String> error, ModelMap map) {
 	public String getAuthErrorPage(ModelMap map) {
 		prepareMap(map);
 		map.put("application_name", environment.getProperty("spring.application.name"));
+		map.put("mainPage", ServletUriComponentsBuilder.fromCurrentContextPath().build().toUriString());
 		return "auth-error";
 	}
 

src/main/resources/templates/auth-error.html

@@ -39,6 +39,7 @@
 		<h2>An error occurred during the authentication procedure.</h2>
 		<p><b>If you are a user of <span th:text="${application_name}"></span>:</b> please report this issue to your administrator and try to log out from your Identity Provider.</p>
 		<p><b>If you are an administrator of <span th:text="${application_name}"></span>:</b> this error page is typically shown because of an configuration error in the authentication setup. See the logs for more information.</p>
+		<a th:href="${mainPage}">Go back to the main page</a>
 	</div>
 
 <style>
@@ -50,4 +51,4 @@ <h2>An error occurred during the authentication procedure.</h2>
 
 </body>
 
-</html>
+</html>