Add ClientAuthenticationMethod#toString

Closes gh-13497

Author: jzheaux

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/AbstractWebClientReactiveOAuth2AccessTokenResponseClient.java

@@ -115,8 +115,7 @@ private void validateClientAuthenticationMethod(T grantRequest) {
 		if (!supportedClientAuthenticationMethod) {
 			throw new IllegalArgumentException(String.format(
 					"This class supports `client_secret_basic`, `client_secret_post`, and `none` by default. Client [%s] is using [%s] instead. Please use a supported client authentication method, or use `set/addParametersConverter` or `set/addHeadersConverter` to supply an instance that supports [%s].",
-					clientRegistration.getRegistrationId(), clientAuthenticationMethod.getValue(),
-					clientAuthenticationMethod.getValue()));
+					clientRegistration.getRegistrationId(), clientAuthenticationMethod, clientAuthenticationMethod));
 		}
 	}
 

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/ClientAuthenticationMethodValidatingRequestEntityConverter.java

@@ -41,7 +41,7 @@ public RequestEntity<?> convert(T grantRequest) {
 				|| clientAuthenticationMethod.equals(ClientAuthenticationMethod.CLIENT_SECRET_POST);
 		Assert.isTrue(supportedClientAuthenticationMethod, () -> String.format(
 				"This class supports `client_secret_basic`, `client_secret_post`, and `none` by default. Client [%s] is using [%s] instead. Please use a supported client authentication method, or use `setRequestEntityConverter` to supply an instance that supports [%s].",
-				registrationId, clientAuthenticationMethod.getValue(), clientAuthenticationMethod.getValue()));
+				registrationId, clientAuthenticationMethod, clientAuthenticationMethod));
 		return this.delegate.convert(grantRequest);
 	}
 

oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/ClientAuthenticationMethod.java

@@ -98,4 +98,9 @@ public int hashCode() {
 		return getValue().hashCode();
 	}
 
+	@Override
+	public String toString() {
+		return this.value;
+	}
+
 }