feat(security): start negotiation when a rpc connection is established

[levy5307]

When a rpc connection is established, if the configuration of open_auth is true, we should start negotiation by creating a negotiation instance for both server rpc_session and client rpc_session.
Especially for client rpc_session, we should change the connect state to SS_NEGOTIATION, which means we are doing security authentication.

 negotiation process:

                                                client                   server
                                                     |---   SASL_LIST_MECHANISMS    -->|
                                                     |<-- SASL_LIST_MECHANISMS_RESP ---|
                                                     |---  SASL_SELECT_MECHANISMS  --->|
                                                     |<-- SASL_SELECT_MECHANISMS_OK ---|
                                                     |                                 |
                                                     |------    SASL_INITIATE   ------>|
                                                     |                                 |
                                                     |<----     SASL_CHALLENGE    -----|
                                                     |-----      SASL_RESPONSE    ---->|
                                                     |                                 |
                                                     |              .....              |
                                                     |                                 |
                                                     |<----     SASL_CHALLENGE    -----|
                                                     |-----      SASL_RESPONSE    ---->|
                                                     |                                 |        (authentication will succeed
                                                     |                                 |          if all chanllenges passed)
                                                     | <---        SASL_SUCC      -----|
    (client won't response                           |                                 |
          if servers says ok)                        |                                 |
                                                     | ----         RPC_CALL      ---> |
                                                     | <---         RPC_RESP       ----|

New configuration added

[security]
+ enable_auth = false

[hycdong]

Could you please explain the negotiation process with its function or structure to me? For example, when open_auth is true, should create negotiation with both client and server rpc session, client will turn its state to SS_NEGOTIATION, then start to negotiation by function start_negotiate. How about server rpc session, when will server call function start_negotiate?
Besides, is the SS_NEGOTIATION only used for client session?

[levy5307]

Could you please explain the negotiation process with its function or structure to me? For example, when open_auth is true, should create negotiation with both client and server rpc session, client will turn its state to SS_NEGOTIATION, then start to negotiation by function start_negotiate. How about server rpc session, when will server call function start_negotiate?
Besides, is the SS_NEGOTIATION only used for client session?

1. Server need to call start_negotiation to create server_negotiation and change it's state to SASL_LIST_MECHANISMS.
2. All states in session_state is only used by client, including session_state, to do some state judgement.
3. Here is the negotiation process, And I will add it in the next pull request:

 negotiation process:

                                                client                                                                          server
                                                     |    ---        SASL_LIST_MECHANISMS         -->  |
                                                     |   <--  SASL_LIST_MECHANISMS_RESP   ---  |
                                                     |   ---       SASL_SELECT_MECHANISMS     --->|
                                                     |  <--   SASL_SELECT_MECHANISMS_OK ---  |
                                                     |                                                                                       |
                                                     |  -----------        SASL_INITIATE       ------------> |
                                                     |                                                                                       |
                                                     |  <----------     SASL_CHALLENGE   ------------- |
                                                     | ------------       SASL_RESPONSE    -----------> |
                                                     |                                                                                       |
                                                     |                                        .....                                         |
                                                     |                                                                                       |
                                                     |  <----------     SASL_CHALLENGE   ------------- |
                                                     | ------------       SASL_RESPONSE    -----------> |
                                                     |                                                                                       |        (authentication will succeed
                                                     |                                                                                       |           if all chanllenges passed)
                                                     | <-----------            SASL_SUCC      --------------- |
    (client won't response   |                                                                                       |
          if servers says ok)       |                                                                                       |
                                                     | ------------               RPC_CALL        -------------> |
                                                     | <----------                RPC_RESP        -------------- |