Deprecate usages of RestTemplate and Provide Alternative (e.g. RestClient)

[jgrandja]

RestTemplate was @Deprecated via spring-projects/spring-framework#36574 and is marked for removal in 8.0.

We need to deprecate all usages of RestTemplate and provide RestClient alternatives.

[therepanic]

Hi, @jgrandja. Can I work on it?

[jgrandja]

@therepanic I need to create sub-issues for each usage of RestTemplate. I will do this after we release 7.1 and then will assign you a sub-issue.