Implement SAML Authentication

[jumarmartin]

• added new path for SAML support, "/saml"

• removed identity as this is no longer required due to samlsp.RequireAccount middleware (maybe)

• naïvely generated key/cert, added skeleton for possible pass-in-flag-or-env-var

• added initializeSaml to services initializer

• rename Services -> svc in main.go

• improved make run in ods/backend to support local dev without building docker container

• cleaned up go.mod

[jumarmartin]

(abridged from https://github.com/crewjam/saml#getting-started-as-a-service-provider)

• inside of the backend fodler, create a X.509 keypair using the following command: openssl req -x509 -newkey rsa:2048 -keyout myservice.key -out myservice.cert -days 365 -nodes -subj "/CN=myservice.example.com"

• run the following command to generate a metadata file: mdpath=saml-test-$USER-$HOST.xml \ curl localhost:8000/saml/metadata > $mdpath

• upload the metadata file to https://samltest.id/upload.php

• browse to localhost:3000/affiliate

• login through samltest.id (same pattern of Elon's login feature)