Introduce JdbcTokenStore

[boyan-velinov]

Expected Behavior

Introduce JdbcTokenStore, as the one in Spring Security OAuth 2.x

Current Behavior

Missing way to cache tokens in stateless app running in several instance.

Context

Currently we are using JdbcTokenStore, provided by Spring Security OAuth 2.x, in order to cache the tokens, which later on are used to accomplish long running processes on behalf of the user.

Here is the current application setup:

• App is running on several instances in Cloud Foundry
• App uses postgre as backing service
• App receives oauth tokens
• App acts on behalf of the user, by using the tokens, to call Cloud Controller. Actual computing and external calls can be done on different app instances.

More details and code snippets can be found in the stackoverflow question: https://stackoverflow.com/questions/65904062/tokenstore-in-spring-security-5-x-after-removal-of-spring-security-oauth-2-x

[jgrandja]

@boyan-velinov This has already been implemented in 5.3.0 via JdbcOAuth2AuthorizedClientService. See #7655 and #7889