Some SP clients might be confused by using a standard SAML protocol tag
<Extensions> which is used for signed REDIRECT binding messages to
specify signing key ID. To enable the interoperability, generation of
the tag is disabled by default and can be enabled for individual
clients.
Contrary to POST binding, signature of SAML protocol message sent using
REDIRECT binding is contained in query parameters and not in the
message. This renders <dsig:KeyName> key ID hint unusable. This commit
adds <Extensions> element in SAML protocol message containing key ID so
that key ID is present in the SAML protocol message.
Changes of SAML assertion creation/parsing that are required to allow
for validation of rotating realm key: signed SAML assertions and signed
SAML protocol message now contain signing key ID in XML <dsig:KeyName>
element.
Moved methods `transformUserInfoToken`, `transformAccessToken`,
`transformIDToken` to the `AbstractOIDCProtocolMapper` base class
in order to reduce code duplication.
Previously every mapper implemented at least one or two of those
methods with exactly the same code.
Having those methods in the base class ensures that the code is the
same for all mappers. Since the mentioned methods are declared
on the `OIDCIDTokenMapper`, `OIDCAccessTokenMapper` and `UserInfoTokenMapper`
interfaces `AbstractOIDCProtocolMapper` implementations can now choose
how they should be handled by the `TokenManager`
by implementing the desired set of interfaces `*TokenMapper`-interfaces.
I think this provides a good balance between ease of use, reduced code duplication
and ensured backwards compatiblity.
Existing protocol mapper implementations will still work since they just implement
their own logic for `transformUserInfoToken`, `transformAccessToken`,
`transformIDToken`.
The "claim" information provided by a `ProtocolMapper` to a `*Token` can now
be provided by overriding the `AbstractOIDCProtocolMapper.setClaim` method.
Adapted all eligible ProtocolMapper implementations within the
`org.keycloak.protocol.oidc.mappers` package accordingly.
