Attribute Resolver Name

[Rod Widdowson]

I've just checked in the code to introduce the reloadable attribute
resolver; one interesting issue has arisen - the attribute resolver is now
anonymous.  This is because the AttributeResolverType is non identified.

In V2 we get over this by using the spring bean id, but with the new
infrastructure this no longer exists - the ResolveAttribute Action interacts
with the ser

My proposal is to add an option Id attribute to AttributeResolverType and
use this, and default this to "shibboleth.AttributeResolver" in the parser,
that way existing configurations will see no difference,  and advance
configurations with multiple attribute resolvers (has anyone done this?)
will not be penalized.  This is a forward compatible change to the schema -
and we are proposing another one shortly.

As a couple of asides:
1) I tried using the description from the input Resource as the name but
that is ugly, and ungainly and not really what the user needs:

DEBUG [net.shibboleth.idp.attribute.resolver.AttributeResolverImpl:429] -
Attribute Resolver 'from class path resource
[net/shibboleth/idp/attribute/resolver/spring/attribute-resolver.xml]':
removing result of attribute definition telephoneNumber, it's attribute
contains no values

2) The attribute filter does not suffer from this issue since the
<afp:AttributeFilterPolicyGroupType> is identified.