[Test🧪] Add unit tests for the Topic deletion request and result classification

Prerequisites

• I have searched existing test issues

Test Scope

Crate: rocketmq-admin-core
File: rocketmq-tools/rocketmq-admin/rocketmq-admin-core/src/core/topic/deletion.rs
Coverage: the file has no test module at all, and no tests/ file covers it

src/core/topic/deletion.rs is 280 lines and has no #[cfg(test)] module. The
integration tests under tests/ do not cover it either:
tests/batch_admin_delete.rs exercises DeleteTopicsInBrokerRequest and
DeleteSubscriptionGroupsRequest, which are different types in different modules.

The file holds one validated request and one result classifier:

// line 41
    pub fn try_new(topic: impl Into<String>, cluster_name: Option<String>) -> Result<Self> {
        let topic = topic.into();
        let topic = topic.trim();
        if !TopicValidator::validate_topic(topic).valid() {
            return Err(invalid_request());
        }
        let cluster_name = cluster_name
            .map(|name| name.trim().to_owned())
            .filter(|name| !name.is_empty())
            .ok_or_else(invalid_request)?;
        // ...
    }

// line 58
    pub fn with_optional_namesrv_addr(mut self, namesrv_addr: Option<String>) -> Self {
        self.namesrv_addr = namesrv_addr
            .map(|addr| addr.trim().to_owned())
            .filter(|addr| !addr.is_empty());
        self
    }

// lines 106, 110 and 121
    pub fn is_complete_success(&self) -> bool {
        self.failures.is_empty() && self.name_server_deleted
    }

    pub fn is_partial_failure(&self) -> bool {
        !self.broker_addrs.is_empty() && (!self.failures.is_empty() || !self.name_server_deleted)
    }

    pub fn ensure_complete(&self) -> Result<()> {
        // ... permission denied when the first failure says so, otherwise a broker operation error
    }

ensure_complete is the projection the adapter uses to turn a partial result into
a status, and it branches on the first failure's error_code string. None of that
branching is pinned by a test.

This module is behind no feature gate for the request type, so the tests run with
cargo test -p rocketmq-admin-core on default features. validated, further down
the file, is gated on #[cfg(any(feature = "client-adapter", test))], so it is
also reachable from a test module.

Test Cases

Add a #[cfg(test)] mod tests block at the end of
src/core/topic/deletion.rs with use super::*;.

DeleteTopicRequest::try_new:

• A valid topic and cluster are accepted, and topic() and cluster_name()
  return the trimmed values for input such as (" TopicA ", Some(" cluster-a ")).
• A None cluster name is rejected.
• A cluster name of "" and of " " is both rejected.
• An invalid topic is rejected, for example one containing / or : which
  TopicValidator::validate_topic refuses.
• Every rejection returns core.argument.invalid, asserted as
  error.descriptor().code().as_str() == "core.argument.invalid".

with_optional_namesrv_addr:

• Some(" 127.0.0.1:9876 ") is stored trimmed.
• Some(" ") and None both leave namesrv_addr() as None.

DeleteTopicResult::is_complete_success and is_partial_failure:

• No failures and name_server_deleted == true is a complete success, and it
  is not a partial failure.
• No failures and name_server_deleted == false is not a complete success. Add
  a case with at least one broker address and assert whether it counts as a
  partial failure, recording the current answer.
• A result with an empty broker_addrs is never a partial failure, even when
  it has failures, and a comment records that rule.

DeleteTopicResult::ensure_complete:

• A complete success returns Ok(()).
• A failure whose error_code is "BROKER_PERMISSION_DENIED" returns an
  error with code auth.permission.denied.
• A failure whose error_code is "auth.permission.denied" returns the same
  code, pinning that both spellings are accepted.
• Only the first failure is inspected: put a non-permission failure first
  and a permission failure second, and assert the returned code is the broker
  operation error rather than the permission error.
• Any other incomplete result returns the broker operation error code.

Willing to contribute?

• I can submit a PR for this

Acceptance Criteria

• src/core/topic/deletion.rs gains a #[cfg(test)] mod tests block covering
  every case above.
• The production types and functions are unchanged. These tests pin current
  behaviour; if a case looks wrong, raise it in the issue thread.
• cargo test -p rocketmq-admin-core topic::deletion passes.

Validation

Run from the repository root:

cargo fmt -p rocketmq-admin-core -- --check
cargo test -p rocketmq-admin-core topic::deletion
cargo test -p rocketmq-admin-core

Start in rocketmq-tools/rocketmq-admin/rocketmq-admin-core/src/core/topic/deletion.rs and read the request constructors and result classification methods around the referenced lines. Add the #[cfg(test)] module with the listed validation, trimming, classification, and first-failure cases. Run cargo fmt -p rocketmq-admin-core -- --check, then cargo test -p rocketmq-admin-core topic::deletion and the full crate test suite.