Add permission security snippets for permission skill

[strzyzkat]

Adds code snippets and XML resources for the security module demonstrating Android permission security best practices and caller identity validation. These snippets ground the android-permission-security skill in tested, linted, and compiled code.

Changes made:

• Custom Signature Permissions: Demonstrates signature protection levels for private inter-app communication in AndroidManifest.xml.
• Known Signer Permissions (API 31+): Adds knownSigner permission configuration with certificate digest verification in security_certs.xml and AndroidManifest.xml.
• Caller Validation (AppAuthenticator): Implements CallerVerifier.kt using Jetpack androidx.security:security-app-authenticator configured via allowed_peers.xml.
• Runtime Permission Workflow: Adds RuntimePermissionsActivity.kt implementing modern ActivityResultContracts.RequestPermission and educational rationale checks (shouldShowRequestPermissionRationale).
• Protected Broadcasts: Demonstrates permission-guarded broadcast dispatch, Android 14+ sender identity opt-in (BroadcastOptions.setShareIdentityEnabled), and receiver verification in ProtectedBroadcastSnippets.kt.
• Binder IPC Method Checks: Implements FineGrainedBoundService.kt using enforceCallingPermission for method-level read/write permission segregation.
• Content Provider Protection: Configures distinct readPermission (knownSigner) and writePermission (signature) in AndroidManifest.xml.
• Error Handling & Signature Verification: Implements PermissionErrorHandling.kt demonstrating SecurityException handling and UID certificate checks via PackageManager.hasSigningCertificate.

[snippet-bot]

Here is the summary of changes.

You are about to add 17 region tags.

• security/src/main/AndroidManifest.xml:32, tag android_security_custom_permission_signature_manifest
• security/src/main/AndroidManifest.xml:38, tag android_security_custom_permission_known_signer_manifest
• security/src/main/AndroidManifest.xml:45, tag android_security_content_provider_read_write_manifest
• security/src/main/AndroidManifest.xml:92, tag android_security_custom_permission_service_manifest
• security/src/main/AndroidManifest.xml:103, tag android_security_known_signer_service_manifest
• security/src/main/AndroidManifest.xml:114, tag android_security_protected_broadcast_receiver_manifest
• security/src/main/AndroidManifest.xml:129, tag android_security_provider_read_write_manifest
• security/src/main/java/com/example/snippets/security/permissions/CallerVerifier.kt:23, tag android_security_caller_verifier_app_authenticator
• security/src/main/java/com/example/snippets/security/permissions/FineGrainedBoundService.kt:30, tag android_security_service_enforce_calling_permission
• security/src/main/java/com/example/snippets/security/permissions/PermissionErrorHandling.kt:30, tag android_security_permission_error_handling
• security/src/main/java/com/example/snippets/security/permissions/PermissionErrorHandling.kt:55, tag android_security_caller_signature_verification
• security/src/main/java/com/example/snippets/security/permissions/ProtectedBroadcastSnippets.kt:27, tag android_security_protected_broadcast_send
• security/src/main/java/com/example/snippets/security/permissions/ProtectedBroadcastSnippets.kt:35, tag android_security_broadcast_sender_identity
• security/src/main/java/com/example/snippets/security/permissions/ProtectedBroadcastSnippets.kt:54, tag android_security_broadcast_receiver_verify_identity
• security/src/main/java/com/example/snippets/security/permissions/RuntimePermissionsActivity.kt:24, tag android_security_runtime_permission_request
• security/src/main/res/values/security_certs.xml:18, tag android_security_known_signer_certs_xml
• security/src/main/res/xml/allowed_peers.xml:18, tag android_security_allowed_peers_xml

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