Add some target fields and move some things around (#3879)

In preparation for putting proxy code in the api package this creates some necessary fields in the target output and it pre-moves credential parsing and proxy handshake code to their new places. This will make the diff for the actual proxy code move quite a bit smaller.

Co-authored-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>

api/targets/session_authorization_data.gen.go

@@ -0,0 +1,28 @@
+// Code generated by "make api"; DO NOT EDIT.
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package targets
+
+import (
+	"time"
+
+	"github.com/hashicorp/boundary/api/scopes"
+)
+
+type SessionAuthorizationData struct {
+	SessionId         string            `json:"session_id,omitempty"`
+	TargetId          string            `json:"target_id,omitempty"`
+	Scope             *scopes.ScopeInfo `json:"scope,omitempty"`
+	CreatedTime       time.Time         `json:"created_time,omitempty"`
+	Type              string            `json:"type,omitempty"`
+	ConnectionLimit   int32             `json:"connection_limit,omitempty"`
+	EndpointPort      uint32            `json:"endpoint_port,omitempty"`
+	Expiration        time.Time         `json:"expiration,omitempty"`
+	Certificate       []byte            `json:"certificate,omitempty"`
+	PrivateKey        []byte            `json:"private_key,omitempty"`
+	HostId            string            `json:"host_id,omitempty"`
+	Endpoint          string            `json:"endpoint,omitempty"`
+	WorkerInfo        []*WorkerInfo     `json:"worker_info,omitempty"`
+	DefaultClientPort uint32            `json:"default_client_port,omitempty"`
+}