fix: Removing custom SSL cert verification from RefResolver

- **Remote Schema Resolution**: Automatically fetches and parses external schema definitions over HTTP/HTTPS

- **Performance Optimization**: Caches fetched schemas to avoid redundant network requests

- **Reliability**: Implements configurable timeouts to prevent hanging on slow or unresponsive endpoints

- **Security**: Uses SSL certificate validation with proper certificate store configuration

- **Error Handling**: Provides clear error messages for network failures, timeouts, and invalid JSON responses

## How to Use

## Implementation Details

- Only HTTP and HTTPS schemes are supported. Other schemes (FTP, file://, etc.) will raise an error.

- The resolver configures SSL certificate validation using the system's default certificate store with the `PARTIAL_CHAIN` flag, which validates certificate chains and expiration while being more lenient with certain certificate configurations.

- The class-level cache is shared across all instances. In multi-threaded environments, consider using appropriate synchronization mechanisms if cache consistency is critical.

          uri.host,

          uri.port,

          use_ssl: uri.scheme == 'https',

          cert_store: ssl_cert_store,

          open_timeout: @timeout_s,

          read_timeout: @timeout_s

        ) do |http|

      rescue SocketError, Errno::ECONNREFUSED => e

        raise(JSONSchemer::UnknownRef, "Connection failed for #{uri_str}: #{e.message}")

      end

      def ssl_cert_store

        store = OpenSSL::X509::Store.new

        store.set_default_paths

        # This still validates the certificate chain and expiration,

        # just not explicitly revoked certs

        store.flags = OpenSSL::X509::V_FLAG_PARTIAL_CHAIN

        store

      rescue StandardError

        nil

      end

    end

  end

end