MM-18356: Adds ability to paginate channel search. (#12830)

* MM-18356: Adds ability to paginate channel search.

* MM-18356: Minor refactor.

* MM-18356: Adds doc.

* MM-18356: Fixes doc.

* MM-18356: Some commentary, adds the total count to non-paginated responses, and removes a stray fmt.

* MM-18356: Fixes shadowed variable.

* MM-18356: Removes paginate field and API parameter.

* MM-18356: Adds method to check if channel search is a paginated request.

* MM-18356: Vet fix.

api4/channel.go

@@ -908,9 +908,11 @@ func searchAllChannels(c *Context, w http.ResponseWriter, r *http.Request) {
 		NotAssociatedToGroup:   props.NotAssociatedToGroup,
 		ExcludeDefaultChannels: props.ExcludeDefaultChannels,
 		IncludeDeleted:         r.URL.Query().Get("include_deleted") == "true",
+		Page:                   props.Page,
+		PerPage:                props.PerPage,
 	}
 
-	channels, err := c.App.SearchAllChannels(props.Term, opts)
+	channels, totalCount, err := c.App.SearchAllChannels(props.Term, opts)
 	if err != nil {
 		c.Err = err
 		return
@@ -918,7 +920,16 @@ func searchAllChannels(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	// Don't fill in channels props, since unused by client and potentially expensive.
 
-	w.Write([]byte(channels.ToJson()))
+	var payload []byte
+
+	if props.Page != nil && props.PerPage != nil {
+		data := model.ChannelsWithCount{Channels: channels, TotalCount: totalCount}
+		payload = data.ToJson()
+	} else {
+		payload = []byte(channels.ToJson())
+	}
+
+	w.Write(payload)
 }
 
 func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {

api4/channel_test.go

@@ -1075,6 +1075,24 @@ func TestSearchAllChannels(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 }
 
+func TestSearchAllChannelsPaged(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+	Client := th.Client
+
+	search := &model.ChannelSearch{Term: th.BasicChannel.Name}
+	search.Term = ""
+	search.Page = model.NewInt(0)
+	search.PerPage = model.NewInt(2)
+	channelsWithCount, resp := th.SystemAdminClient.SearchAllChannelsPaged(search)
+	CheckNoError(t, resp)
+	require.Len(t, *channelsWithCount.Channels, 2)
+
+	search.Term = th.BasicChannel.Name
+	_, resp = Client.SearchAllChannels(search)
+	CheckForbiddenStatus(t, resp)
+}
+
 func TestSearchGroupChannels(t *testing.T) {
 	th := Setup().InitBasic()
 	defer th.TearDown()