Centralized configuration for JDBC driver

[zhicwu]

Summary

Centralized configuration for JDBC driver, which might be of use when you want to maintain consistent configuration for a group of users using JDBC driver v0.4.2+. Please pay attention that it's built for ease of use not security control.

Usage

• add custom server setting

  <!-- config.xml -->
  <custom_settings_prefixes>custom_</custom_settings_prefixes>
  
  <!-- users.xml -->
  <profiles>
      ...
      <managed>
          <!-- use '*' to discard all options specified in JDBC client -->
          <custom_jdbc_config><![CDATA['*&custom_settings=max_result_rows%3D1&compress_algorithm=gzip&!transactionSupport']]></custom_jdbc_config>
      </managed>
  </profiles>
  <users>
      ...
      <user1>
          <profile>managed</profile>
          <networks>
              <ip>::/0</ip>
          </networks>
          <password>123</password>
          <quota>default</quota>
      </user1>
  </users>

• connect to the server using JDBC driver as usual

  Properties props = new Properties();
  props.setProperty("user", "user1");
  props.setProperty("password", "123");
  try (Connection conn = DriverManager.getConnection("jdbc:ch:http://server1?transactionSupport&max_execution_time=3600")) {
      // same as connecting to below URL
      // jdbc:ch:http://server1?custom_settings=max_result_rows%3D1&compress_algorithm=gzip&!transactionSupport
  }

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials