[IMPROVE] SAML implementation (#17742)

...teor-accounts-saml/server/definition/IAttributeMapping.ts

...unts-saml/server/definition/IAuthorizeRequestVariables.ts

...ccounts-saml/server/definition/ILogoutRequestVariables.ts

...meteor-accounts-saml/server/definition/ILogoutResponse.ts

...counts-saml/server/definition/ILogoutResponseVariables.ts

...eor-accounts-saml/server/definition/IMetadataVariables.ts

app/meteor-accounts-saml/server/definition/ISAMLAction.ts

app/meteor-accounts-saml/server/definition/ISAMLAssertion.ts

...or-accounts-saml/server/definition/ISAMLGlobalSettings.ts

app/meteor-accounts-saml/server/definition/ISAMLRequest.ts

app/meteor-accounts-saml/server/definition/ISAMLUser.ts

...ccounts-saml/server/definition/IServiceProviderOptions.ts

app/meteor-accounts-saml/server/definition/callbacks.ts

app/meteor-accounts-saml/server/index.js

app/meteor-accounts-saml/server/lib/SAML.ts

app/meteor-accounts-saml/server/lib/ServiceProvider.ts

app/meteor-accounts-saml/server/lib/Utils.ts

app/meteor-accounts-saml/server/lib/constants.ts

...r-accounts-saml/server/lib/generators/AuthorizeRequest.ts

...teor-accounts-saml/server/lib/generators/LogoutRequest.ts