public Builder httpHeader(String key, String value) {
            this.configuration.put(ClientConfigProperties.httpHeader(key), value);
            return this;
        }
Defines list of headers that should be sent with each request. The Client will use a header value
defined in {@code headers} instead of any other.
Operation settings may override these headers.

@see InsertSettings#httpHeaders(Map)
@see QuerySettings#httpHeaders(Map)
@see CommandSettings#httpHeaders(Map)
@param key - a name of the header.
@param value - a value of the header.
@return same instance of the builder
client-v2/src/main/java/com/clickhouse/client/api/Client.java