Retrieves the URI to the named resource. This can be used, for example, to locate configuration
or authority files. The resource should be declared in the <externalResourceDependencies>
section of the descriptor.
This method is safer than
#getResourceURL(String) in its treatment of file paths
containing spaces. This is because the
URI#getPath() does perform URL decoding of that
path (decoding %20 sequences to spaces) whereas
URL#getPath() does not.
For backwards compatibility, if the key is not declared as a resource dependency, it is looked
up directly in the
#getDataPath() and the class path. However, this usage is
deprecated and support may be dropped in future versions. ALL external resource dependencies
should be declared in the descriptor.