[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/permissions_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/mattermost/mattermost-server/v6/model"
 )
@@ -20,23 +21,24 @@ func TestGetAncillaryPermissions(t *testing.T) {
 	t.Run("Valid Case, Passing in SubSection Permissions", func(t *testing.T) {
 		subsectionPermissions = []string{model.PermissionSysconsoleReadReportingSiteStatistics.Id}
 		expectedAncillaryPermissions = []string{model.PermissionGetAnalytics.Id}
-		actualAncillaryPermissions, resp := th.Client.GetAncillaryPermissions(subsectionPermissions)
-		CheckNoError(t, resp)
+		actualAncillaryPermissions, _, err := th.Client.GetAncillaryPermissions(subsectionPermissions)
+		require.NoError(t, err)
 		assert.Equal(t, append(subsectionPermissions, expectedAncillaryPermissions...), actualAncillaryPermissions)
 	})
 
 	t.Run("Invalid Case, Passing in SubSection Permissions That Don't Exist", func(t *testing.T) {
 		subsectionPermissions = []string{"All", "The", "Things", "She", "Said", "Running", "Through", "My", "Head"}
 		expectedAncillaryPermissions = []string{}
-		actualAncillaryPermissions, resp := th.Client.GetAncillaryPermissions(subsectionPermissions)
-		CheckNoError(t, resp)
+		actualAncillaryPermissions, _, err := th.Client.GetAncillaryPermissions(subsectionPermissions)
+		require.NoError(t, err)
 		assert.Equal(t, append(subsectionPermissions, expectedAncillaryPermissions...), actualAncillaryPermissions)
 	})
 
 	t.Run("Invalid Case, Passing in nothing", func(t *testing.T) {
 		subsectionPermissions = []string{}
 		expectedAncillaryPermissions = []string{}
-		_, resp := th.Client.GetAncillaryPermissions(subsectionPermissions)
+		_, resp, err := th.Client.GetAncillaryPermissions(subsectionPermissions)
+		require.Error(t, err)
 		CheckBadRequestStatus(t, resp)
 	})
 }