feign-mock is too strict with request headers when matching requests

I am using https://github.com/OpenFeign/feign/tree/master/mock to write unit tests. When one would want to match/verify request headers, the current implementation seems too strict as it checks for exact equality. Ideally, it should be matching a subset of the headers as there can be headers the tester doesn't care about or generated headers like Content-Length.

I know the workaround for this is to write a RequestInterceptor and do assertions there, but that is not ideal as it adds a lot of boilerplate code in tests. For each test, one needs to write a test-specific RequestInterceptor.

I would like to propose making the header matching in RequestKey.java#L171 match a subset of the headers instead of exact equality.

Bonus Request: match with RegEx

Start in mock/src/main/java/feign/mock/RequestKey.java at the header comparison around line 171. Review how request headers are matched and define done as allowing expected headers to be a subset while preserving existing matching behavior; treat the separately marked regex request as additional scope.