Adds Shared Channel related API endpoints (#27436)

* Adds Shared Channel management API endpoints

New endpoints for the following routes are added:

- Get Shared Channel Remotes by Remote Cluster at `GET
/api/v4/remotecluster/{remote_id}/sharedchannelremotes`
- Invite Remote Cluster to Channel at `POST
/api/v4/remotecluster/{remote_id}/channels/invite`
- Uninvite Remote Cluster to Channel at `POST
/api/v4/remotecluster/{remote_id}/channels/uninvite`

These endpoints are planned to be used from the system console, and
gated through the `manage_secure_connections` permission.

* Adds i18n messages for API errors

* Fix pagination flaky test

* Fix linter

* Adds the posibility of filtering shared channel remotes by home

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/client4.go

@@ -572,6 +572,14 @@ func (c *Client4) remoteClusterRoute() string {
 	return "/remotecluster"
 }
 
+func (c *Client4) sharedChannelRemotesRoute(remoteId string) string {
+	return fmt.Sprintf("%s/%s/sharedchannelremotes", c.remoteClusterRoute(), remoteId)
+}
+
+func (c *Client4) channelRemoteRoute(remoteId, channelId string) string {
+	return fmt.Sprintf("%s/%s/channels/%s", c.remoteClusterRoute(), remoteId, channelId)
+}
+
 func (c *Client4) sharedChannelsRoute() string {
 	return "/sharedchannels"
 }
@@ -8887,6 +8895,57 @@ func (c *Client4) DeleteRemoteCluster(ctx context.Context, remoteClusterId strin
 	return BuildResponse(r), nil
 }
 
+func (c *Client4) GetSharedChannelRemotesByRemoteCluster(ctx context.Context, remoteId string, excludeHome, excludeRemote bool, page, perPage int) ([]*SharedChannelRemote, *Response, error) {
+	v := url.Values{}
+	if excludeHome {
+		v.Set("exclude_home", "true")
+	}
+	if excludeRemote {
+		v.Set("exclude_remote", "true")
+	}
+	if page != 0 {
+		v.Set("page", fmt.Sprintf("%d", page))
+	}
+	if perPage != 0 {
+		v.Set("per_page", fmt.Sprintf("%d", perPage))
+	}
+	url := c.sharedChannelRemotesRoute(remoteId)
+	if len(v) > 0 {
+		url += "?" + v.Encode()
+	}
+
+	r, err := c.DoAPIGet(ctx, url, "")
+	if err != nil {
+		return nil, BuildResponse(r), err
+	}
+	defer closeBody(r)
+
+	var scs []*SharedChannelRemote
+	json.NewDecoder(r.Body).Decode(&scs)
+
+	return scs, BuildResponse(r), nil
+}
+
+func (c *Client4) InviteRemoteClusterToChannel(ctx context.Context, remoteId, channelId string) (*Response, error) {
+	url := fmt.Sprintf("%s/invite", c.channelRemoteRoute(remoteId, channelId))
+	r, err := c.DoAPIPost(ctx, url, "")
+	if err != nil {
+		return BuildResponse(r), err
+	}
+	defer closeBody(r)
+	return BuildResponse(r), nil
+}
+
+func (c *Client4) UninviteRemoteClusterToChannel(ctx context.Context, remoteId, channelId string) (*Response, error) {
+	url := fmt.Sprintf("%s/uninvite", c.channelRemoteRoute(remoteId, channelId))
+	r, err := c.DoAPIPost(ctx, url, "")
+	if err != nil {
+		return BuildResponse(r), err
+	}
+	defer closeBody(r)
+	return BuildResponse(r), nil
+}
+
 func (c *Client4) GetAncillaryPermissions(ctx context.Context, subsectionPermissions []string) ([]string, *Response, error) {
 	var returnedPermissions []string
 	url := fmt.Sprintf("%s/ancillary", c.permissionsRoute())

server/public/model/shared_channel.go

@@ -263,6 +263,8 @@ type SharedChannelRemoteFilterOpts struct {
 	ChannelId       string
 	RemoteId        string
 	InclUnconfirmed bool
+	ExcludeHome     bool
+	ExcludeRemote   bool
 }
 
 // SyncMsg represents a change in content (post add/edit/delete, reaction add/remove, users).