api: create AuthDialer and ProtocolDialer

To disable SSL by default we want to transfer
`OpenSslDialer` to the go-openssl repository.
In order to do so, we need to minimize the amount of
copy-paste of the private functions.

`AuthDialer` is created as a dialer-wrapper, that
calls authentication methods.
`ProtoDialer` is created to check the `ProtocolInfo`
in the created connection.

`NoAuth` constant is added for dialers, that do not
require authentication

Part of #301

CHANGELOG.md

@@ -37,6 +37,9 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
   the response (#237)
 - Ability to mock connections for tests (#237). Added new types `MockDoer`,
   `MockRequest` to `test_helpers`.
+- `AuthDialer` and `ProtocolDialer` types for creating a dialer with
+  authentication and `ProtocolInfo` check (#301)
+- `NoAuth` constant for dialers that do not require authentication (#301)
 
 ### Changed
 

auth.go

@@ -27,6 +27,9 @@ const (
 	// available only for the Tarantool Enterprise Edition (EE) with
 	// SSL transport.
 	PapSha256Auth
+
+	// NoAuth is used when no authentication is needed.
+	NoAuth Auth = 1 << 15
 )
 
 // String returns a string representation of an authentication method.
@@ -38,6 +41,8 @@ func (a Auth) String() string {
 		return chapSha1
 	case PapSha256Auth:
 		return papSha256
+	case NoAuth:
+		return "no-auth"
 	default:
 		return fmt.Sprintf("unknown auth type (code %d)", a)
 	}

auth_test.go

@@ -17,6 +17,7 @@ func TestAuth_String(t *testing.T) {
 		{AutoAuth, "auto"},
 		{ChapSha1Auth, "chap-sha1"},
 		{PapSha256Auth, "pap-sha256"},
+		{NoAuth, "no-auth"},
 		{Auth(unknownId), fmt.Sprintf("unknown auth type (code %d)", unknownId)},
 	}
 

connection.go

@@ -440,7 +440,9 @@ func (conn *Connection) dial(ctx context.Context) error {
 	}
 
 	conn.addr = c.Addr()
-	conn.Greeting.Version = c.Greeting().Version
+	connGreeting := c.Greeting()
+	conn.Greeting.Version = connGreeting.Version
+	conn.Greeting.Salt = connGreeting.Salt
 	conn.serverProtocolInfo = c.ProtocolInfo()
 
 	spaceAndIndexNamesSupported :=