GTNPORTAL-3506 Allow multiple apps registering the very same AMD paths

Can you double-check or confirm that you indeed mean `newPrefixesToContextPaths` and `newPrefixesToTargetPaths` on line 148? It seems you check `available.value`, which is from `newPrefixesToTargetPaths`, but then say that it exists on `newPrefixesToContextPaths` and throw the exception. It might indeed be the right thing, but seems like a possible bug :-)