This PR implements a comprehensive fine-grained permissions data infrastructure for the GitHub PowerShell module, enabling detection of GitHub App installations that may be missing newly added permissions.

• Fixes 🩹 [Patch]: Fine-Grained Permissions Data for GitHub PowerShell Module #485

What's New

GitHubPermission Class

Added a new public GitHubPermission class with the following properties:

• Name - Programmatic permission name (e.g., contents, issues)
• DisplayName - Human-friendly name (e.g., "Contents", "Issues")
• Description - Brief description of what access the permission grants
• URL - Link to relevant GitHub documentation
• Options - Available access levels (read, write, admin)
• Type - Permission type (Fine-grained, Classic)
• Scope - Application scope (Repository, Organization, User, Enterprise)

Comprehensive Permissions Database

Added 90 fine-grained permissions covering all major GitHub permission categories:

• 33 Repository permissions - actions, contents, issues, pull_requests, secrets, etc.
• 33 Organization permissions - members, administration, organization_secrets, etc.
• 18 User permissions - profile, followers, git_ssh_keys, etc.
• 6 Enterprise permissions - custom properties, organization installation, etc.

Get-GitHubPermissionDefinition Function

New public function to query the permissions database with advanced filtering:

# Get all permissions
Get-GitHubPermissionDefinition

# Filter by scope
Get-GitHubPermissionDefinition -Scope Repository

# Combined filtering
Get-GitHubPermissionDefinition -Type Fine-grained -Scope Organization

# Find specific permissions
Get-GitHubPermissionDefinition -Name 'contents'

Argument Completers

Added argument completers for Get-GitHubPermissionDefinition parameters to improve user experience:

• Name - Tab completion for available permission names (actions, contents, issues, etc.)
• DisplayName - Tab completion for available permission display names (Actions, Dependabot alerts, etc.)
• Type - Tab completion for available permission types (Fine-grained)
• Scope - Tab completion for available scopes (Repository, Organization, User, Enterprise)

Use Cases

This infrastructure enables several key scenarios:

1. Permission Validation - Compare GitHub App installations against the complete permissions list
2. Installation Health Checks - Detect apps missing newly added permissions
3. Documentation - Provide users with comprehensive permission reference
4. Automation - Build tools that ensure installations stay current with permission requirements
5. Enhanced User Experience - Tab completion for parameter values improves usability

Implementation Details

• File path permissions excluded - These are handled differently by the GitHub API (appear under FilePaths property rather than as named permissions)
• Maintainable structure - Easy to update when GitHub adds new permissions
• Performance optimized - Efficient filtering and lookup operations
• Comprehensive testing - Full test coverage for all functionality
• Argument completion - Improves user experience with tab completion support

Example Usage

# Check what repository permissions are available (with tab completion)
$repoPerms = Get-GitHubPermissionDefinition -Scope <TAB>
Write-Host "Repository permissions: $($repoPerms.Count)"

# Get details about the contents permission (with tab completion)
$contents = Get-GitHubPermissionDefinition -Name cont<TAB>
Write-Host "$($contents.DisplayName): $($contents.Description)"
Write-Host "Available options: $($contents.Options -join ', ')"

This provides the foundation for building automated permission management tools and ensuring GitHub App installations remain up-to-date with the latest permission requirements.