Use Spring Boot default RestClient metrics to get insights on our usage

[henrybley]

When using Spring Boot RestClient, it should normally expose certain metrics about the calls it is making. We can leverage these metrics to create a dashboard where we create insights into how many api calls we are doing to the GitHub API.

Ideas for panels:

• A total number of calls within a certain time range
• A graph displaying the amount of calls over time
• Average response times over time.

E.g. calls/sec, avg and max time, number of errors

[henrybley]

https://docs.spring.io/spring-framework/reference/integration/observability.html#observability.http-client