ITT-2234 - Handle user impersonation settings

lib/auth/types/AuthType.js

lib/auth/types/basicauth/BasicAuth.js

lib/auth/types/jwt/Jwt.js

lib/auth/types/openid/OpenId.js

lib/auth/types/proxycache/ProxyCache.js

lib/auth/types/saml/Saml.js

lib/backend/searchguard.js

lib/session/sessionPlugin.js