Configurable no-overlap checking

[raynay-r]

For my use-case I need to load services dynamically from different JARs. I do this similar to the SerializationWhitelist, where I put a File into META-INF/services. Since the services i want to load come from different package I have multiple of these files with the same name, which is prevent by the no-overlap rule/check.

Here you make an exception for SerializationWhitelist, but prevent any other services from being loaded:
https://github.com/corda/corda/blob/ec92801904183ac92a75d62288c20b86dc879509/core/src/main/kotlin/net/corda/core/serialization/internal/AttachmentsClassLoader.kt#L147-#L161

Would it be possible to make a new configuration parameter which allows the user to supply a list of interface names which should be allowed to overlap? I really need this in my project and if you are willing to make the change I could try and provide a pull request.

[nargas-ritu]

Created CORDA-4188 for review