Prior to this commit, the implementation of equals() in EncodedResource
was based solely on the resource and encoding. Thus, if a Charset were
specified instead of an encoding, invocations of equals() would not
work as expected.
This commit addresses this issue by including the charset in the
implementation of equals() and introducing corresponding tests in a new
EncodedResourceTests class. Furthermore, this commit makes
EncodedResource immutable and updates all Javadoc to reflect support
for the encoding and charset properties.
Issue: SPR-12767
93c70b7440