Introduced ReactiveAuthenticationManagerResolver

Suitable for multi-tenant reactive applications needing to branch
authentication strategies based on request details.

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

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2002-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.authentication;
+
+import org.springframework.security.authentication.ReactiveAuthenticationManager;
+
+import reactor.core.publisher.Mono;
+
+/**
+ * An interface for resolving a {@link ReactiveAuthenticationManager} based on the provided context
+ *
+ * @author Rafiullah Hamedy
+ * @since 5.2
+ */
+@FunctionalInterface
+public interface ReactiveAuthenticationManagerResolver<C> {
+	Mono<ReactiveAuthenticationManager> resolve(C context);
+}