feat: add data source to get organization members' SAML/SCIM linked identities

[jsifuentes]

Resolves #1794

Behavior

• Adds a new data source github_organization_external_identities that queries the GraphQL API for the SAML linked identity for organization members.

The github_organization data source returns members, but the email returned in members is the user's public GitHub e-mail. In my case, I want to be able to associate an organization member's GitHub username to their SAML-linked work e-mail. This allows me to reference their work e-mail in Terraform configurations and get their GitHub username for things like repo permissions.

--

This is the GraphQL query:

query {
  organization(login: $organization) {
    samlIdentityProvider {
      externalIdentities(first: 100, after: $after) {
        edges {
          node {
            user {
              login
            }
            samlIdentity {
              nameId
              username
              givenName
              familyName
            }
            scimIdentity {
              username
              givenName
              familyName
            }
          }
        }
      }
    }
  }
}

---

Additional info

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Added the appropriate label for the given change

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

Pull request type

Feature/model/API additions: Type: Feature

[felixlut]

LGTM overall, it's just the question about the nesting of the fields I'm questioning somewhat. It's not a hill I'd die on, I'm fine either way

[felixlut]

LGTM overall, it's just the question about the nesting of the fields I'm questioning somewhat. It's not a hill I'd die on though, I'm fine either way

Ignore my comment, it was me being wrong. LGTM!

[kfcampbell]

Thank you!