Add API endpoint for accessing repo topics (#7963)

* Create API endpoints for repo topics.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Generate swagger

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Add documentation to functions

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Grammar fix

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix function comment

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Can't use FindTopics when looking for a single repo topic, as it doesnt use exact match

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Add PUT ​/repos​/{owner}​/{repo}​/topics and remove GET ​/repos​/{owner}​/{repo}​/topics

* Ignore if topic is sent twice in same request, refactoring.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix topic dropdown with api changes.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Style fix

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Update API documentation

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Better way to handle duplicate topics in slice

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Make response element TopicName an array of strings, instead of using an array of TopicName

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Add test cases for API Repo Topics.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix format of tests

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix comments

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix unit tests after adding some more topics to the test fixture.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Update models/topic.go

Limit multiple if else if ...

Co-Authored-By: Antoine GIRARD <sapk@users.noreply.github.com>

* Engine as first parameter in function

Co-Authored-By: Antoine GIRARD <sapk@users.noreply.github.com>

* Replace magic numbers with http status code constants.

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix variable scope

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Test one read with login and one with token

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Add some more tests

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Apply suggestions from code review

Use empty struct for efficiency

Co-Authored-By: Lauris BH <lauris@nix.lv>

* Add test case to check access for user with write access

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Fix access, repo admin required to change topics

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Correct first test to be without token

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

* Any repo reader should be able to access topics.

* No need for string pointer

Signed-off-by: David Svantesson <davidsvantesson@gmail.com>

modules/structs/repo_topic.go

@@ -0,0 +1,29 @@
+// Copyright 2019 The 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 structs
+
+import (
+	"time"
+)
+
+// TopicResponse for returning topics
+type TopicResponse struct {
+	ID        int64     `json:"id"`
+	Name      string    `json:"topic_name"`
+	RepoCount int       `json:"repo_count"`
+	Created   time.Time `json:"created"`
+	Updated   time.Time `json:"updated"`
+}
+
+// TopicName a list of repo topic names
+type TopicName struct {
+	TopicNames []string `json:"topics"`
+}
+
+// RepoTopicOptions a collection of repo topic names
+type RepoTopicOptions struct {
+	// list of topic names
+	Topics []string `json:"topics"`
+}