Move sdk structs to modules/structs (#6905)

* move sdk structs to moduels/structs

* fix tests

* fix fmt

* fix swagger

* fix vendor

modules/structs/user_key.go

@@ -0,0 +1,23 @@
+// Copyright 2015 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package structs
+
+import (
+	"time"
+)
+
+// PublicKey publickey is a user key to push code to repository
+type PublicKey struct {
+	ID          int64  `json:"id"`
+	Key         string `json:"key"`
+	URL         string `json:"url,omitempty"`
+	Title       string `json:"title,omitempty"`
+	Fingerprint string `json:"fingerprint,omitempty"`
+	// swagger:strfmt date-time
+	Created  time.Time `json:"created_at,omitempty"`
+	Owner    *User     `json:"user,omitempty"`
+	ReadOnly bool      `json:"read_only,omitempty"`
+	KeyType  string    `json:"key_type,omitempty"`
+}