[API] generalize list header (#16551)

* Add info about list endpoints to CONTRIBUTING.md

* Let all list endpoints return X-Total-Count header 

* Add TODOs for GetCombinedCommitStatusByRef

* Fix models/issue_stopwatch.go

* Rrefactor models.ListDeployKeys

* Introduce helper func and use them for SetLinkHeader related func

integrations/api_repo_topic_test.go

@@ -7,6 +7,7 @@ package integrations
 import (
 	"fmt"
 	"net/http"
+	"net/url"
 	"testing"
 
 	"code.gitea.io/gitea/models"
@@ -15,6 +16,38 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestAPITopicSearch(t *testing.T) {
+	defer prepareTestEnv(t)()
+	searchURL, _ := url.Parse("/api/v1/topics/search")
+	var topics struct {
+		TopicNames []*api.TopicResponse `json:"topics"`
+	}
+
+	query := url.Values{"page": []string{"1"}, "limit": []string{"4"}}
+
+	searchURL.RawQuery = query.Encode()
+	res := MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 4)
+	assert.EqualValues(t, "6", res.Header().Get("x-total-count"))
+
+	query.Add("q", "topic")
+	searchURL.RawQuery = query.Encode()
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	assert.Len(t, topics.TopicNames, 2)
+
+	query.Set("q", "database")
+	searchURL.RawQuery = query.Encode()
+	res = MakeRequest(t, NewRequest(t, "GET", searchURL.String()), http.StatusOK)
+	DecodeJSON(t, res, &topics)
+	if assert.Len(t, topics.TopicNames, 1) {
+		assert.EqualValues(t, 2, topics.TopicNames[0].ID)
+		assert.EqualValues(t, "database", topics.TopicNames[0].Name)
+		assert.EqualValues(t, 1, topics.TopicNames[0].RepoCount)
+	}
+}
+
 func TestAPIRepoTopic(t *testing.T) {
 	defer prepareTestEnv(t)()
 	user2 := models.AssertExistsAndLoadBean(t, &models.User{ID: 2}).(*models.User) // owner of repo2