Fix: add client-side URL length validation to satisfy test_too_long_uri

[kindler-king]

Metadata

• Reference Issue: Fixes Adding client-side URL length validation to fix failing test_too_long_uri #1481
• New Tests Added: No (existing test_too_long_uri covers this)
• Documentation Updated: No
• Change Log Entry: "Add client-side URL length validation in _send_request() to handle overly long URLs and fix test_too_long_uri."

Details

This PR adds a client-side URL length validation step to _send_request() in openml/_api_calls.py.
The goal is to prevent extremely long URLs from being sent to the server and to ensure that
test_too_long_uri behaves as expected.

🧩 What problem does this fix?

Currently, when a very long list of data_ids is provided (e.g., 10,000 IDs):

1. The constructed URL becomes extremely long.
2. The client sends the request to the server.
3. The server returns HTTP 414 (“Request-URI Too Long”) with an HTML error page.
4. This HTML triggers an XML parse error, which is wrapped into a generic:

🛠️ What does this PR change?

This PR adds a fail-fast check before any network request is made:

MAX_URL_LENGTH = 2000
if len(url) > MAX_URL_LENGTH:
 raise OpenMLServerError("URI too long!")

This ensures:

1. No server request is made
2. Deterministic client behavior regardless of server config
3. Test test_too_long_uri passes
4. Better user experience and reduced server load
5. The fallback 414 handling in __parse_server_exception() remains unchanged.

✔ Test Status

1. test_too_long_uri now passes.
2. Full test suite passes locally.