Implement PAP-SHA256 auth mechanism

[oleg-jukovec]

We need to support a new authorization mechanizm PAP-SHA256, RFC:

https://www.notion.so/tarantool/Authentication-methods-908501aa74834bdea70c384d6df97105

We need:

1. To add Opts.AuthType to force 'chap-sha1' or 'pap-sha256' authorization method here:
   

   go-tarantool/connection.go

   Line 215 in d6d0031

   type Opts struct {

2. To check IPROTO_AUTH_TYPE = 0x5bhere:
   

   go-tarantool/response.go

   Lines 195 to 210 in d6d0031

   	case KeyVersion:
   	if err = d.Decode(&serverProtocolInfo.Version); err != nil {
   	return err
   	}
   	case KeyFeatures:
   	if larr, err = d.DecodeArrayLen(); err != nil {
   	return err
   	}
   	serverProtocolInfo.Features = make([]ProtocolFeature, larr)
   	for i := 0; i < larr; i++ {
   	if err = d.Decode(&feature); err != nil {
   	return err
   	}
   	serverProtocolInfo.Features[i] = feature
   	}

   
   and add the information about auth type to IdRequest response.
3. To choose an authorization method by priority: Opts.AuthType -> IPROTO_AUTH_TYPE -> 'chap-sha1' (default).
4. To implement the method pap-sha256 for authReques according to the RFC:
   https://github.com/tarantool/go-tarantool/blob/d6d0031d7a0ce9959edf57f9407bba9652a37506/auth.go
   

   go-tarantool/request.go

   Lines 598 to 603 in d6d0031

   	func (req *authRequest) Body(res SchemaResolver, enc *encoder) error {
   	return enc.Encode(map[uint32]interface{}{
   	KeyUserName: req.user,
   	KeyTuple: []interface{}{string("chap-sha1"), string(req.scramble)},
   	})
   	}

The connector should refuse to use PAP-SHA256 unless the network channel is encrypted with SSL/TLS.

Linked issues:

tarantool/tarantool#7987
tarantool/tarantool#7988
tarantool/tarantool#7989
https://github.com/tarantool/tarantool-ee/issues/295
https://github.com/tarantool/enterprise_doc/issues/206

[LeonidVas]

To be implemented in the EE-version of the connector.

[LeonidVas]

The bosses turn the wheel one more time. We implement this feature here.