Reduce the logging level of the "normal" errors.

It's expected that request will be made that are missing parameters and are made for invalid registration IDs. So they are errors, but they aren't a proper internal error that needs investigating like other exceptions.

src/main/java/uk/ac/ox/ctl/lti13/security/oauth2/client/lti/web/OAuth2AuthorizationRequestRedirectFilter.java

@@ -205,14 +205,14 @@ private boolean hasNoPlatform(HttpServletRequest request) {
 	private void unsuccessfulRedirectForAuthorization(HttpServletRequest request, HttpServletResponse response,
                                                       Exception failed) throws IOException, ServletException {
 
-		if (logger.isErrorEnabled()) {
-			logger.error("Authorization Request failed: " + failed.toString(), failed);
-		}
 		if (failed instanceof InvalidInitiationRequestException) {
+			logger.info("Invalid initiation request: "+ failed);
 			response.sendError(HttpStatus.BAD_REQUEST.value(), failed.getMessage());
 		} else if (failed instanceof InvalidClientRegistrationIdException) {
+			logger.info("Invalid registration ID: "+ failed);
 			response.sendError(HttpStatus.NOT_FOUND.value(), failed.getMessage());
 		} else {
+			logger.error("Authorization Request failed: " + failed.toString(), failed);
 			response.sendError(HttpStatus.INTERNAL_SERVER_ERROR.value(), HttpStatus.INTERNAL_SERVER_ERROR.getReasonPhrase());
 		}
 	}