fix(client): allow hostnames in server address configuration

[felixfaisal]

Which issue does this PR close?

Closes #2882

Rationale

Server address validation previously required a literal socket address, preventing the use of DNS hostnames. This change allows hostnames (e.g., localhost:8080) in addition to IP addresses.

What changed?

Server address validation previously relied on SocketAddr parsing, which only accepts literal IP addresses and rejected DNS hostnames (e.g., localhost:8080). This prevented using hostnames when configuring client connections.

Validation now uses ToSocketAddrs, which performs address resolution and returns the list of socket addresses for a given host. TcpStream::connect(...) already performs this resolution internally and attempts to connect to each resolved address.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. Which tools? ChatGPT free version
2. Scope of usage? Write documentations like comments
3. How did you verify the generated code works correctly?

• I built the code using cargo build
• I ran the unit tests under TCPConfigBuilder and added an additional unit test, also modifying another
• I then ran the server and ran the examples

4. Can you explain every line of the code if asked? Yup

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 70.08%. Comparing base (261d255) to head (b515b76).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...ebsocket_config/websocket_client_config_builder.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2923      +/-   ##
============================================
- Coverage     70.08%   70.08%   -0.01%     
  Complexity      776      776              
============================================
  Files          1028     1028              
  Lines         85279    85282       +3     
  Branches      62653    62668      +15     
============================================
+ Hits          59771    59772       +1     
+ Misses        22980    22977       -3     
- Partials       2528     2533       +5     

Flag	Coverage Δ
csharp	67.43% <ø> (-0.19%)	⬇️
go	36.37% <ø> (ø)
java	56.26% <ø> (ø)
node	91.37% <ø> (-0.07%)	⬇️
python	81.43% <ø> (ø)
rust	70.66% <87.50%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...figuration/tcp_config/tcp_client_config_builder.rs	67.70% <100.00%> (+2.11%)	⬆️
...ebsocket_config/websocket_client_config_builder.rs	0.00% <0.00%> (ø)

... and 15 files with indirect coverage changes

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[hubcio]

hey, thanks for the pr! the intent is solid but there's a fundamental issue with the approach.

to_socket_addrs() calls getaddrinfo() under the hood, which is a synchronous blocking dns lookup. doing this inside build() means config construction now requires network access and can block the thread for seconds if dns is slow. config builders hould be pure/deterministic - th quic builder already gets this right by doing zero address validation in build(). we cannot accept this resolution.

validate the format only (valid host:port structure, port is a valid u16) and leave actual dns resolution to connect time. TcpStream::connect already does resolution internally anyway.