Polish SAML 2.0 Authentication Builder

Issue gh-17861

Author: jzheaux

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/authentication/Saml2AssertionAuthentication.java

@@ -23,6 +23,7 @@
 
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.saml2.provider.service.registration.RelyingPartyRegistration;
 import org.springframework.util.Assert;
 
 /**
@@ -78,8 +79,7 @@ public Builder<?> toBuilder() {
 	}
 
 	/**
-	 * A builder preserving the concrete {@link Authentication} type
-	 *
+	 * A builder of {@link Saml2AssertionAuthentication} instances
 	 * @since 7.0
 	 */
 	public static class Builder<B extends Builder<B>> extends Saml2Authentication.Builder<B> {
@@ -94,6 +94,12 @@ protected Builder(Saml2AssertionAuthentication token) {
 			this.relyingPartyRegistrationId = token.relyingPartyRegistrationId;
 		}
 
+		/**
+		 * Use these credentials.
+		 * They must be of type {@link Saml2ResponseAssertionAccessor}.
+		 * @param credentials the credentials to use
+		 * @return the {@link Builder} for further configurations
+		 */
 		@Override
 		public B credentials(@Nullable Object credentials) {
 			Assert.isInstanceOf(Saml2ResponseAssertionAccessor.class, credentials,
@@ -103,6 +109,12 @@ public B credentials(@Nullable Object credentials) {
 			return (B) this;
 		}
 
+		/**
+		 * Use this registration id
+		 * @param relyingPartyRegistrationId the {@link RelyingPartyRegistration#getRegistrationId}
+		 * to use
+		 * @return the {@link Builder} for further configurations
+		 */
 		public B relyingPartyRegistrationId(String relyingPartyRegistrationId) {
 			this.relyingPartyRegistrationId = relyingPartyRegistrationId;
 			return (B) this;