Fix transparent SSO enforcement for deploy tokens

Drew Blessingrequested to merge
dblessing_transparent_sso_deploy_token into master

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Fixes #378928 (closed)

Implements #group_sso?(group) method on the DeployToken PolicyActor and adds tests. The failure was noticed in Staging when :transparent_sso_enforcement was enabled.

NoMethodError: undefined method `group_sso?' for #<DeployToken:0x00007f574ae72c20>
Did you mean?  groups
  from activemodel (6.1.6.1) lib/active_model/attribute_methods.rb:469:in `method_missing'
  from ee/lib/gitlab/auth/group_saml/sso_enforcer.rb:51:in `saml_enforced?'
  from ee/lib/gitlab/auth/group_saml/sso_enforcer.rb:29:in `access_restricted?'
  from ee/lib/gitlab/auth/group_saml/sso_enforcer.rb:41:in `group_access_restricted?'
  from ee/app/policies/ee/group_policy.rb:540:in `sso_enforcement_prevents_access?'
  from ee/app/policies/ee/group_policy.rb:88:in `block (2 levels) in <module:GroupPolicy>'

We seem to have an existing paradigm where we add methods to PolicyActor which is included in DeployToken so that deploy tokens can behave like users (or at least respond to the same methods).

I did not add a Changelog since this only occurs when :transparent_sso_enforcement feature flag is enabled, and it's currently default disabled.

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Edited by Drew Blessing

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