feat: Add GitHub App Enterprise perm scope

[eroullit]

This pull request adds support for several new enterprise-related permission fields to the InstallationPermissions struct, along with corresponding accessor methods and unit tests. These changes enhance the codebase to handle a wider range of GitHub App installation permissions, particularly for enterprise features.

Creating a installation token yields this output when enterprise-scope permissions are used:

{
"token": "ghs_etcetc",
"expires_at": "2026-06-30T14:28:23Z",
"permissions": {
"enterprise_ai_controls": "read",
"enterprise_copilot_metrics": "read",
"enterprise_credentials": "read",
"enterprise_custom_enterprise_roles": "read",
"enterprise_custom_org_roles": "read",
"enterprise_custom_properties": "read",
"enterprise_custom_properties_for_organizations": "read",
"enterprise_organizations": "write",
"enterprise_organization_installations": "read",
"enterprise_organization_installation_repositories": "read",
"enterprise_people": "read",
"enterprise_sso": "read",
"enterprise_teams": "read"
},
"repository_selection": "selected"
}

Previously, these information were omitted when go-github is in used.

Enterprise permissions support:

• Added new fields to the InstallationPermissions struct for various enterprise-related permissions, such as EnterpriseAIControls, EnterpriseCopilotMetrics, EnterpriseCredentials, and others. (github/apps.go)
• Implemented getter methods for each new enterprise permission field to safely retrieve their values. (github/github-accessors.go)

Testing:

• Added unit tests for each new getter method to ensure correct behavior when fields are set, unset, or the struct is nil. (github/github-accessors_test.go)

[google-cla]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.50%. Comparing base (7a388ca) to head (c8d798e).
⚠️ Report is 10 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #4343 +/- ##
=======================================
Coverage 97.50% 97.50% =======================================
Files 193 193 Lines 19451 19481 +30 =======================================
+ Hits 18965 18995 +30 
Misses 269 269 Partials 217 217 

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[eroullit]

Hi @gmlewis 👋

I did register for an individual CLA triggering an the new contributor update does not seem to proceed 🙏

[eroullit]

Linter fails at:

"EnterpriseAIControls" to "EnterpriseAiControls"

Artificial Intelligence (AI) is universally capitalized.

[alexandear]

To fix it, add "AI": true, to the list of initialisms

go-github/tools/structfield/structfield.go

Line 412 in 7a388ca

varinitialisms=map[string]bool{

Keep the list sorted.

[eroullit]

Added with c8d798e

[gmlewis]

Thank you, @eroullit!
LGTM.

cc: @alexandear