Description

Replace the misleading read-only error used for unsupported operations on the audit database with a more accurate message:

Apache IoTDB does not support this operation on database '%s'.

The message is shared by the tree-model and table-model authorization paths and is localized in both English and Chinese.

This PR also fixes the internal audit writer exemption in TreeAccessCheckVisitor. The check now compares INTERNAL_AUDIT_USER with the request username instead of the target path.

Affected operations

• Apply the new message to tree-model write, schema, template, TTL, and database deletion checks that previously reported the audit database as read-only.
• Apply the same message to unsupported table-model operations on __audit.
• Keep the existing reserved-name, grant/revoke, and AUDIT-admin query messages unchanged because they already describe their restrictions precisely.
• Preserve writes from the internal audit user while rejecting external writes to root.__audit.

Test coverage

• Add coverage for DELETE DATABASE root.__audit and template operations in IoTDBTemplateAuthIT.
• Update TTL coverage in IoTDBSeriesPermissionIT.
• Add coverage for DROP DATABASE __audit in IoTDBAuthenticationTableIT.
• Add a focused unit test for internal audit writes, external audit writes, and writes to ordinary paths.

Verified with:

• mvn spotless:apply -pl iotdb-core/datanode
• IoTDBTemplateAuthIT#manageDataBaseTest
• IoTDBSeriesPermissionIT#ttlOperationsTest
• git diff --check

This PR has:

• been self-reviewed.
• added comments explaining the intent where it was not obvious.
• added or updated unit and integration tests.
• been tested in a test IoTDB cluster.

Key changed/added classes (or packages if there are too many classes) in this PR

• AccessControlImpl
• ITableAuthCheckerImpl
• TreeAccessCheckVisitor
• DataNodeQueryMessages
• TreeAccessTest