Implement brand image endpoints for APIv4 (#5733)

* Implement brand image endpoints for APIv4

* Fix unit test

model/client4.go

@@ -190,6 +190,10 @@ func (c *Client4) GetLdapRoute() string {
 	return fmt.Sprintf("/ldap")
 }
 
+func (c *Client4) GetBrandRoute() string {
+	return fmt.Sprintf("/brand")
+}
+
 func (c *Client4) DoApiGet(url string, etag string) (*http.Response, *AppError) {
 	return c.DoApiRequest(http.MethodGet, url, "", etag)
 }
@@ -1498,3 +1502,49 @@ func (c *Client4) TestLdap() (bool, *Response) {
 		return CheckStatusOK(r), BuildResponse(r)
 	}
 }
+
+// Brand Section
+
+// GetBrandImage retrieves the previously uploaded brand image.
+func (c *Client4) GetBrandImage() ([]byte, *Response) {
+	if r, err := c.DoApiGet(c.GetBrandRoute()+"/image", ""); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else if data, err := ioutil.ReadAll(r.Body); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: NewAppError("GetBrandImage", "model.client.read_file.app_error", nil, err.Error(), r.StatusCode)}
+	} else {
+		return data, BuildResponse(r)
+	}
+}
+
+// UploadBrandImage sets the brand image for the system.
+func (c *Client4) UploadBrandImage(data []byte) (bool, *Response) {
+	body := &bytes.Buffer{}
+	writer := multipart.NewWriter(body)
+
+	if part, err := writer.CreateFormFile("image", "brand.png"); err != nil {
+		return false, &Response{Error: NewAppError("UploadBrandImage", "model.client.set_profile_user.no_file.app_error", nil, err.Error(), http.StatusBadRequest)}
+	} else if _, err = io.Copy(part, bytes.NewBuffer(data)); err != nil {
+		return false, &Response{Error: NewAppError("UploadBrandImage", "model.client.set_profile_user.no_file.app_error", nil, err.Error(), http.StatusBadRequest)}
+	}
+
+	if err := writer.Close(); err != nil {
+		return false, &Response{Error: NewAppError("UploadBrandImage", "model.client.set_profile_user.writer.app_error", nil, err.Error(), http.StatusBadRequest)}
+	}
+
+	rq, _ := http.NewRequest("POST", c.ApiUrl+c.GetBrandRoute()+"/image", bytes.NewReader(body.Bytes()))
+	rq.Header.Set("Content-Type", writer.FormDataContentType())
+	rq.Close = true
+
+	if len(c.AuthToken) > 0 {
+		rq.Header.Set(HEADER_AUTH, c.AuthType+" "+c.AuthToken)
+	}
+
+	if rp, err := c.HttpClient.Do(rq); err != nil {
+		return false, &Response{StatusCode: http.StatusForbidden, Error: NewAppError(c.GetBrandRoute()+"/image", "model.client.connecting.app_error", nil, err.Error(), http.StatusForbidden)}
+	} else if rp.StatusCode >= 300 {
+		return false, &Response{StatusCode: rp.StatusCode, Error: AppErrorFromJson(rp.Body)}
+	} else {
+		defer closeBody(rp)
+		return CheckStatusOK(rp), BuildResponse(rp)
+	}
+}