developer: enable saml plugin for developers by default

Deploydb with a -P developer profile will run developer-prefill, in that we
enable the SAML plugin by default but only for developers

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
SAMLMetaDataResponse: this should extend AuthenticationCmdResponse

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>