[MM-24987] Dont call GetSchemeRolesForChannel and instead load the scheme from channel (#14514)

* MM-24987 Dont call a.GetSchemeRolesForChannel and instead load the scheme using the channel directly

* Trigger CI

* MM-24987 Add a test for concurrent patch to channel moderation

* MM-24987 Cleanup

app/channel_test.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"sort"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -1657,6 +1658,52 @@ func TestPatchChannelModerationsForChannel(t *testing.T) {
 			}
 		})
 	}
+
+	t.Run("Handles concurrent patch requests gracefully", func(t *testing.T) {
+		addCreatePosts := []*model.ChannelModerationPatch{
+			{
+				Name: &createPosts,
+				Roles: &model.ChannelModeratedRolesPatch{
+					Members: model.NewBool(false),
+					Guests:  model.NewBool(false),
+				},
+			},
+		}
+		removeCreatePosts := []*model.ChannelModerationPatch{
+			{
+				Name: &createPosts,
+				Roles: &model.ChannelModeratedRolesPatch{
+					Members: model.NewBool(false),
+					Guests:  model.NewBool(false),
+				},
+			},
+		}
+
+		wg := sync.WaitGroup{}
+		wg.Add(20)
+		for i := 0; i < 10; i++ {
+			go func() {
+				th.App.PatchChannelModerationsForChannel(channel, addCreatePosts)
+				th.App.PatchChannelModerationsForChannel(channel, removeCreatePosts)
+				wg.Done()
+			}()
+		}
+		for i := 0; i < 10; i++ {
+			go func() {
+				th.App.PatchChannelModerationsForChannel(channel, addCreatePosts)
+				th.App.PatchChannelModerationsForChannel(channel, removeCreatePosts)
+				wg.Done()
+			}()
+		}
+		wg.Wait()
+
+		higherScopedGuestRoleName, higherScopedMemberRoleName, _, _ := th.App.GetTeamSchemeChannelRoles(channel.TeamId)
+		higherScopedMemberRole, _ := th.App.GetRoleByName(higherScopedMemberRoleName)
+		higherScopedGuestRole, _ := th.App.GetRoleByName(higherScopedGuestRoleName)
+		assert.Contains(t, higherScopedMemberRole.Permissions, createPosts)
+		assert.Contains(t, higherScopedGuestRole.Permissions, createPosts)
+	})
+
 }
 
 // TestMarkChannelsAsViewedPanic verifies that returning an error from a.GetUser