[MM-37557] Move error out of client4 response (#18101)

* Return an error seperately from Response

* Remove BuildErrorResponse

* Drop Response.Error from model/client4.go

* Migrate require.Nil checks

* Migrate require.NotNil checks

* More manual fixes

* Move error check out of CheckOKStatus and CheckCreatedStatus

* Move error check out of CheckForbiddenStatus

* Move error check out of CheckUnauthorizedStatus

* Move error check out of CheckNotFoundStatus

* Move error check out of CheckBadRequestStatus

* Move error check out of CheckNotImplementedStatus and CheckRequestEntityTooLargeStatus

* Move error check out of CheckInternalErrorStatus

* Move error check out of CheckServiceUnavailableStatus

* Remove error check from checkHTTPStatus

* Remove remaining references to Response.Error

* Check previously unchecked errors

* Manually fix compile and linter errors

* Return error in CreateWebSocket methods

* Return error instead of *AppError in DoApi methods

* Manually fix bad replacments

* Conistently return Response and error

* Use err instead of seperate bool return value to indicate success

* Reduce ussage of model.AppError in web/oauth_test.go

* Remove client4.Must

* Check error in buf.ReadFrom

* Fix failing tests

api4/cluster_test.go

@@ -16,13 +16,14 @@ func TestGetClusterStatus(t *testing.T) {
 	defer th.TearDown()
 
 	t.Run("as system user", func(t *testing.T) {
-		_, resp := th.Client.GetClusterStatus()
+		_, resp, err := th.Client.GetClusterStatus()
+		require.Error(t, err)
 		CheckForbiddenStatus(t, resp)
 	})
 
 	t.Run("as system admin", func(t *testing.T) {
-		infos, resp := th.SystemAdminClient.GetClusterStatus()
-		CheckNoError(t, resp)
+		infos, _, err := th.SystemAdminClient.GetClusterStatus()
+		require.NoError(t, err)
 
 		require.NotNil(t, infos, "cluster status should not be nil")
 	})
@@ -30,7 +31,8 @@ func TestGetClusterStatus(t *testing.T) {
 	t.Run("as restricted system admin", func(t *testing.T) {
 		th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ExperimentalSettings.RestrictSystemAdmin = true })
 
-		_, resp := th.SystemAdminClient.GetClusterStatus()
+		_, resp, err := th.SystemAdminClient.GetClusterStatus()
+		require.Error(t, err)
 		CheckForbiddenStatus(t, resp)
 	})
 }