MM-21357: Use typed constant for channel types (#17928)

* MM-21357: Use typed constant for channel types

https://mattermost.atlassian.net/browse/MM-21357

```release-note
- Introduced a new type ChannelType for all channel types.
- Updated the Client4.UpdateChannelPrivacy method to ChannelType.
```

* Address review comments

```release-note
NONE
```

* telemetry fix

```release-note
NONE
```

services/sharedchannel/channelinvite.go

@@ -17,15 +17,15 @@ import (
 
 // channelInviteMsg represents an invitation for a remote cluster to start sharing a channel.
 type channelInviteMsg struct {
-	ChannelId            string   `json:"channel_id"`
-	TeamId               string   `json:"team_id"`
-	ReadOnly             bool     `json:"read_only"`
-	Name                 string   `json:"name"`
-	DisplayName          string   `json:"display_name"`
-	Header               string   `json:"header"`
-	Purpose              string   `json:"purpose"`
-	Type                 string   `json:"type"`
-	DirectParticipantIDs []string `json:"direct_participant_ids"`
+	ChannelId            string            `json:"channel_id"`
+	TeamId               string            `json:"team_id"`
+	ReadOnly             bool              `json:"read_only"`
+	Name                 string            `json:"name"`
+	DisplayName          string            `json:"display_name"`
+	Header               string            `json:"header"`
+	Purpose              string            `json:"purpose"`
+	Type                 model.ChannelType `json:"type"`
+	DirectParticipantIDs []string          `json:"direct_participant_ids"`
 }
 
 type InviteOption func(msg *channelInviteMsg)

services/slackimport/parsers.go

@@ -7,10 +7,11 @@ import (
 	"encoding/json"
 	"io"
 
+	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/shared/mlog"
 )
 
-func slackParseChannels(data io.Reader, channelType string) ([]slackChannel, error) {
+func slackParseChannels(data io.Reader, channelType model.ChannelType) ([]slackChannel, error) {
 	decoder := json.NewDecoder(data)
 
 	var channels []slackChannel

services/slackimport/slackimport.go

@@ -31,7 +31,7 @@ type slackChannel struct {
 	Members []string        `json:"members"`
 	Purpose slackChannelSub `json:"purpose"`
 	Topic   slackChannelSub `json:"topic"`
-	Type    string
+	Type    model.ChannelType
 }
 
 type slackChannelSub struct {

services/telemetry/telemetry_test.go

@@ -101,9 +101,9 @@ func initializeMocks(cfg *model.Config) (*mocks.ServerIface, *storeMocks.Store,
 	teamStore.On("GroupSyncedTeamCount").Return(int64(16), nil)
 
 	channelStore := storeMocks.ChannelStore{}
-	channelStore.On("AnalyticsTypeCount", "", "O").Return(int64(25), nil)
-	channelStore.On("AnalyticsTypeCount", "", "P").Return(int64(26), nil)
-	channelStore.On("AnalyticsTypeCount", "", "D").Return(int64(27), nil)
+	channelStore.On("AnalyticsTypeCount", "", model.ChannelTypeOpen).Return(int64(25), nil)
+	channelStore.On("AnalyticsTypeCount", "", model.ChannelTypePrivate).Return(int64(26), nil)
+	channelStore.On("AnalyticsTypeCount", "", model.ChannelTypeDirect).Return(int64(27), nil)
 	channelStore.On("AnalyticsDeletedTypeCount", "", "O").Return(int64(22), nil)
 	channelStore.On("AnalyticsDeletedTypeCount", "", "P").Return(int64(23), nil)
 	channelStore.On("GroupSyncedChannelCount").Return(int64(17), nil)