feat: Add Enterprise SCIM data sources (groups/users)

[vmvarela]

New data sources:

• github_enterprise_scim_groups — GET /scim/v2/enterprises/{enterprise}/Groups (auto-paginates to fetch all results)
• github_enterprise_scim_group — GET /scim/v2/enterprises/{enterprise}/Groups/{scim_group_id}
• github_enterprise_scim_users — GET /scim/v2/enterprises/{enterprise}/Users (auto-paginates to fetch all results)
• github_enterprise_scim_user — GET /scim/v2/enterprises/{enterprise}/Users/{scim_user_id}

Shared helper/types in util_enterprise_scim.go:

• SCIM request builder + Accept: application/scim+json
• SCIM list pagination loop using startIndex/count (exposed as results_per_page, fetch-all by default)
• Full-fidelity flattening for groups/users (meta, members, emails, roles, name, etc.)

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Before the change?

• No support for reading enterprise SCIM entities

After the change?

• Implements: enterprise SCIM read data sources for Groups/Users (list + get).

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[github-actions]

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