Marks the RemoteTeamId field of RemoteClusters as deprecated (#27364)

* Marks the RemoteTeamId field of RemoteClusters as deprecated

The `RemoteTeamId` was used both in the `RemoteCluster` model and as
part of remote invites. It existed so two different remotes could have
multiple secure connections between them, and have each of those
connections scoped to a team, sharing through each only the channels
that belong to their corresponding team.

The way that we're thinking on the feature currently only contemplates
one secure connection between two servers, and shares all the
channels through that secure connection, so this field is no longer
needed.

As we don't have a system in place for the user to choose in which
team a channel should be created from an invite, this change adds a
mechanism that checks the invite for a teamId, and if it's not
present, fetches a team from the database to create the channel
into. This makes the change backwards compatible for secure
connections that already have an established behavior and allows us to
move forward with the implementation of an alternative.

* Mark invite teamId field as deprecated

---------

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

server/public/model/auditconv.go

@@ -750,7 +750,6 @@ func newRemoteCluster(r *RemoteCluster) auditRemoteCluster {
 	var rc auditRemoteCluster
 	if r != nil {
 		rc.RemoteId = r.RemoteId
-		rc.RemoteTeamId = r.RemoteTeamId
 		rc.Name = r.Name
 		rc.DisplayName = r.DisplayName
 		rc.SiteURL = r.SiteURL

server/public/model/remote_cluster.go

@@ -51,7 +51,7 @@ func (bm *Bitmask) UnsetBit(flag Bitmask) {
 
 type RemoteCluster struct {
 	RemoteId     string  `json:"remote_id"`
-	RemoteTeamId string  `json:"remote_team_id"`
+	RemoteTeamId string  `json:"remote_team_id"` // Deprecated: this field is no longer used. It's only kept for backwards compatibility.
 	Name         string  `json:"name"`
 	DisplayName  string  `json:"display_name"`
 	SiteURL      string  `json:"site_url"`
@@ -312,7 +312,7 @@ type RemoteClusterPing struct {
 // RemoteClusterInvite represents an invitation to establish a simple trust with a remote cluster.
 type RemoteClusterInvite struct {
 	RemoteId     string `json:"remote_id"`
-	RemoteTeamId string `json:"remote_team_id"`
+	RemoteTeamId string `json:"remote_team_id"` // Deprecated: this field is no longer used. It's only kept for backwards compatibility.
 	SiteURL      string `json:"site_url"`
 	Token        string `json:"token"`
 }

server/public/model/remote_cluster_test.go

@@ -130,10 +130,9 @@ func TestRemoteClusterInviteEncryption(t *testing.T) {
 
 func makeInvite(url string) RemoteClusterInvite {
 	return RemoteClusterInvite{
-		RemoteId:     NewId(),
-		RemoteTeamId: NewId(),
-		SiteURL:      url,
-		Token:        NewId(),
+		RemoteId: NewId(),
+		SiteURL:  url,
+		Token:    NewId(),
 	}
 }