Enable Null checking in spring-security-cas via JSpecify

Closes gh-16882

core/src/main/java/org/springframework/security/authentication/BadCredentialsException.java

@@ -18,6 +18,8 @@ package org.springframework.security.authentication;
 
 import java.io.Serial;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.security.core.AuthenticationException;
 
 /**
@@ -35,7 +37,7 @@ public class BadCredentialsException extends AuthenticationException {
 	 * Constructs a <code>BadCredentialsException</code> with the specified message.
 	 * @param msg the detail message
 	 */
-	public BadCredentialsException(String msg) {
+	public BadCredentialsException(@Nullable String msg) {
 		super(msg);
 	}
 
@@ -45,7 +47,7 @@ public class BadCredentialsException extends AuthenticationException {
 	 * @param msg the detail message
 	 * @param cause root cause
 	 */
-	public BadCredentialsException(String msg, Throwable cause) {
+	public BadCredentialsException(@Nullable String msg, Throwable cause) {
 		super(msg, cause);
 	}
 

core/src/main/java/org/springframework/security/core/AuthenticationException.java

@@ -50,7 +50,7 @@ public abstract class AuthenticationException extends RuntimeException {
 	 * root cause.
 	 * @param msg the detail message
 	 */
-	public AuthenticationException(String msg) {
+	public AuthenticationException(@Nullable String msg) {
 		super(msg);
 	}