Add SecurityTokenRepository abstraction

Fixes gh-4405

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/token/SecurityTokenRepository.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2017 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
+ *
+ *      http://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.oauth2.client.token;
+
+import org.springframework.security.oauth2.client.authentication.OAuth2AuthenticationToken;
+import org.springframework.security.oauth2.core.SecurityToken;
+
+/**
+ * Implementations of this interface are responsible for the persistence
+ * of {@link SecurityToken}(s) that are associated to an {@link OAuth2AuthenticationToken}.
+ *
+ * @author Joe Grandja
+ * @since 5.0
+ */
+public interface SecurityTokenRepository<T extends SecurityToken> {
+
+	T loadSecurityToken(OAuth2AuthenticationToken authentication);
+
+	void saveSecurityToken(T securityToken, OAuth2AuthenticationToken authentication);
+
+	void removeSecurityToken(OAuth2AuthenticationToken authentication);
+
+}