Adds support for connection_uri GET request

[davidgomes]

This PR adds support for this missing endpoint in Neon's API (https://api-docs.neon.tech/reference/getconnectionuri).

>>> neon.connection_uri('twilight-king-17249571', 'neon_db', 'neondb_owner')
ConnectionUri(uri='postgresql://neondb_owner:bywO1ADn7Mse@ep-ancient-dew-a5la66a7-pooler.us-east-2.aws.neon.tech/neon_db?sslmode=require')

>>> neon.connection_uri('twilight-king-17249571', 'neon_db')
Traceback (most recent call last):
  File "/Users/david/src/neon-api-python/neon_api/client.py", line 117, in _request
    r.raise_for_status()
  File "/Users/david/src/neon-api-python/venv/lib/python3.12/site-packages/requests/models.py", line 1024, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://console.neon.tech/api/v2/projects/twilight-king-17249571/connection_uri?database_name=neon_db

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/david/src/neon-api-python/neon_api/client.py", line 39, in wrapper
    return model(**func(*args, **kwargs))
                   ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/david/src/neon-api-python/neon_api/client.py", line 230, in connection_uri
    return self._request("GET", f"projects/{project_id}/connection_uri", params=r_params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/david/src/neon-api-python/neon_api/client.py", line 119, in _request
    raise NeonAPIError(r.text)
neon_api.exceptions.NeonAPIError: {"code":"","message":"invalid input"}

Also, make test works.