[MM-11593] Prevent user to remove from a direct channel (#9251)

* prevent user to remove from a direct channel

* only allow removing of a member in private or public channel

api4/channel_test.go

@@ -2038,6 +2038,30 @@ func TestRemoveChannelMember(t *testing.T) {
 
 	_, resp = Client.RemoveUserFromChannel(privateChannel.Id, user2.Id)
 	CheckNoError(t, resp)
+
+	// Test on preventing removal of user from a direct channel
+	directChannel, resp := Client.CreateDirectChannel(user1.Id, user2.Id)
+	CheckNoError(t, resp)
+
+	_, resp = Client.RemoveUserFromChannel(directChannel.Id, user1.Id)
+	CheckBadRequestStatus(t, resp)
+
+	_, resp = Client.RemoveUserFromChannel(directChannel.Id, user2.Id)
+	CheckBadRequestStatus(t, resp)
+
+	_, resp = th.SystemAdminClient.RemoveUserFromChannel(directChannel.Id, user1.Id)
+	CheckBadRequestStatus(t, resp)
+
+	// Test on preventing removal of user from a group channel
+	user3 := th.CreateUser()
+	groupChannel, resp := Client.CreateGroupChannel([]string{user1.Id, user2.Id, user3.Id})
+	CheckNoError(t, resp)
+
+	_, resp = Client.RemoveUserFromChannel(groupChannel.Id, user1.Id)
+	CheckBadRequestStatus(t, resp)
+
+	_, resp = th.SystemAdminClient.RemoveUserFromChannel(groupChannel.Id, user1.Id)
+	CheckBadRequestStatus(t, resp)
 }
 
 func TestAutocompleteChannels(t *testing.T) {