Implement GPG related api (#36)

* Implement method for calling gpg related api

gitea/user_gpgkey.go

@@ -0,0 +1,67 @@
+// Copyright 2017 Gitea 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 gitea
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+// GPGKey a user GPG key to sign commit and tag in repository
+type GPGKey struct {
+	ID                int64          `json:"id"`
+	PrimaryKeyID      string         `json:"primary_key_id"`
+	KeyID             string         `json:"key_id"`
+	PublicKey         string         `json:"public_key"`
+	Emails            []*GPGKeyEmail `json:"emails"`
+	SubsKey           []*GPGKey      `json:"subkeys"`
+	CanSign           bool           `json:"can_sign"`
+	CanEncryptComms   bool           `json:"can_encrypt_comms"`
+	CanEncryptStorage bool           `json:"can_encrypt_storage"`
+	CanCertify        bool           `json:"can_certify"`
+	Created           time.Time      `json:"created_at,omitempty"`
+	Expires           time.Time      `json:"expires_at,omitempty"`
+}
+
+// GPGKeyEmail a email attache to a GPGKey
+type GPGKeyEmail struct {
+	Email    string `json:"email"`
+	Verified bool   `json:"verified"`
+}
+
+// CreateGPGKeyOption options create user GPG key
+type CreateGPGKeyOption struct {
+	ArmoredKey string `json:"armored_public_key" binding:"Required"`
+}
+
+// ListMyGPGKeys list all the GPG keys of current user
+func (c *Client) ListMyGPGKeys() ([]*GPGKey, error) {
+	keys := make([]*GPGKey, 0, 10)
+	return keys, c.getParsedResponse("GET", "/user/gpg_keys", nil, nil, &keys)
+}
+
+// GetGPGKey get current user's GPG key by key id
+func (c *Client) GetGPGKey(keyID int64) (*GPGKey, error) {
+	key := new(GPGKey)
+	return key, c.getParsedResponse("GET", fmt.Sprintf("/user/gpg_keys/%d", keyID), nil, nil, &key)
+}
+
+// CreateGPGKey create GPG key with options
+func (c *Client) CreateGPGKey(opt CreateGPGKeyOption) (*GPGKey, error) {
+	body, err := json.Marshal(&opt)
+	if err != nil {
+		return nil, err
+	}
+	key := new(GPGKey)
+	return key, c.getParsedResponse("POST", "/user/gpg_keys", jsonHeader, bytes.NewReader(body), key)
+}
+
+// DeleteGPGKey delete GPG key with key id
+func (c *Client) DeleteGPGKey(keyID int64) error {
+	_, err := c.getResponse("DELETE", fmt.Sprintf("/user/gpg_keys/%d", keyID), nil, nil)
+	return err
+}