MM-48186: Add a new API endpoint to add a user to their default GroupChannels and GroupTeams. (#21591)

* MM-48186: Add a new API endpoint to add a user to their default GroupChannels and GroupTeams.

* MM-48186: Removed unrelated lint fixes.

* MM-48186: Removed variable from previous iteration.

* MM-48186: Adds translation.

* MM-48186: Not upgrading golang.org/x/text in this pr.

* MM-48186: Validate user ID and auth service.

* MM-48186: Use user id from struct.

* MM-48186: Added basic client test.

* MM-48186: Adds empty translation.

* MM-48186: Added translations.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/client4.go

@@ -8458,3 +8458,12 @@ func (c *Client4) GetNewTeamMembersSince(teamID string, timeRange string, page i
 	}
 	return newTeamMembersList, BuildResponse(r), nil
 }
+
+func (c *Client4) AddUserToGroupSyncables(userID string) (*Response, error) {
+	r, err := c.DoAPIPost(c.ldapRoute()+"/users/"+userID+"/group_sync_memberships", "")
+	if err != nil {
+		return BuildResponse(r), err
+	}
+	defer closeBody(r)
+	return BuildResponse(r), nil
+}