Provide ability to compare existing connector configuration to new one

[gunnarmorling]

Say I have a file my-connector1.json, I'd like to easily find out if this differs from an already instantiated connector, and if so, how. The differing configuration attributes (if any) should be marked e.g. in bold in the output.

This could be part of kcctl apply -f my-connector1.json --dry-run probably. Or, more generally speaking, when kcctl apply yields an update to an existing connector (no matter whether dry run or not), any changed attributes should be shown in the response.