Add CorrelationId logic into Spring Starter

One thing that is commonly required in FluentForms app server code is the need for a correlation id (an ID that is optionally provided by a caller that travels with and identifies a particular transaction). We have utilized such code in previous projects, however it would be nice if it could be incorporated into the Spring Boot starter so that it is easy and has a minimal amount of boilerplate code.

It would also be nice if it autoconfigures logging to incorporate the correlation id in all log messages. To do this, it could utilized SLF4J's [Mapped Diagnostic Context](https://www.slf4j.org/manual.html#mdc) (see [here](https://logback.qos.ch/manual/mdc.html) also).