Document JdbcOAuth2AuthorizedClientService

Fixes gh-8061

docs/manual/src/docs/asciidoc/_includes/servlet/appendix/database-schema.adoc

@@ -363,3 +363,26 @@ BEGIN
     SELECT ACL_ENTRY_SQ.NEXTVAL INTO :NEW.ID FROM DUAL;
 END;
 ----
+
+
+[[dbschema-oauth2-client]]
+== OAuth 2.0 Client Schema
+The JDBC implementation of <<oauth2Client-authorized-repo-service, OAuth2AuthorizedClientService>> (`JdbcOAuth2AuthorizedClientService`) requires a table for persisting `OAuth2AuthorizedClient`(s).
+You will need to adjust this schema to match the database dialect you are using.
+
+[source,ddl]
+----
+CREATE TABLE oauth2_authorized_client (
+  client_registration_id varchar(100) NOT NULL,
+  principal_name varchar(200) NOT NULL,
+  access_token_type varchar(100) NOT NULL,
+  access_token_value blob NOT NULL,
+  access_token_issued_at timestamp NOT NULL,
+  access_token_expires_at timestamp NOT NULL,
+  access_token_scopes varchar(1000) DEFAULT NULL,
+  refresh_token_value blob DEFAULT NULL,
+  refresh_token_issued_at timestamp DEFAULT NULL,
+  created_at timestamp DEFAULT CURRENT_TIMESTAMP NOT NULL,
+  PRIMARY KEY (client_registration_id, principal_name)
+);
+----

docs/manual/src/docs/asciidoc/_includes/servlet/oauth2/oauth2-client.adoc

@@ -277,6 +277,13 @@ public class OAuth2ClientController {
 Spring Boot 2.x auto-configuration registers an `OAuth2AuthorizedClientRepository` and/or `OAuth2AuthorizedClientService` `@Bean` in the `ApplicationContext`.
 However, the application may choose to override and register a custom `OAuth2AuthorizedClientRepository` or `OAuth2AuthorizedClientService` `@Bean`.
 
+The default implementation of `OAuth2AuthorizedClientService` is `InMemoryOAuth2AuthorizedClientService`, which stores `OAuth2AuthorizedClient`(s) in-memory.
+
+Alternatively, the JDBC implementation `JdbcOAuth2AuthorizedClientService` may be configured for persisting `OAuth2AuthorizedClient`(s) in a database.
+
+[NOTE]
+`JdbcOAuth2AuthorizedClientService` depends on the table definition described in <<dbschema-oauth2-client, OAuth 2.0 Client Schema>>.
+
 
 [[oauth2Client-authorized-manager-provider]]
 ==== OAuth2AuthorizedClientManager / OAuth2AuthorizedClientProvider