MM-59934: Add Redis to CI and other improvements (#28164)

- Update library version.
- Added MaxFlush delay to help reduce CPU usage.
- Fall back to LRU cache for the caches which use SCAN.
- Added mattermost-redis and running for all api layer
tests in Postgres.

https://mattermost.atlassian.net/browse/MM-59934
```release-note
NONE
```

server/channels/api4/apitestlib.go

@@ -102,6 +102,17 @@ func setupTestHelper(dbStore store.Store, searchEngine *searchengine.Broker, ent
 	*memoryConfig.AnnouncementSettings.AdminNoticesEnabled = false
 	*memoryConfig.AnnouncementSettings.UserNoticesEnabled = false
 	*memoryConfig.PluginSettings.AutomaticPrepackagedPlugins = false
+	// Enabling Redis with Postgres.
+	if *memoryConfig.SqlSettings.DriverName == model.DatabaseDriverPostgres {
+		*memoryConfig.CacheSettings.CacheType = model.CacheTypeRedis
+		redisHost := "localhost"
+		if os.Getenv("IS_CI") == "true" {
+			redisHost = "redis"
+		}
+		*memoryConfig.CacheSettings.RedisAddress = redisHost + ":6379"
+		*memoryConfig.CacheSettings.DisableClientCache = true
+		*memoryConfig.CacheSettings.RedisDB = 0
+	}
 	if updateConfig != nil {
 		updateConfig(memoryConfig)
 	}

server/channels/api4/config_test.go

@@ -515,7 +515,7 @@ func TestUpdateConfigDiffInAuditRecord(t *testing.T) {
 	require.NotEmpty(t, data)
 
 	require.Contains(t, string(data),
-		fmt.Sprintf(`"config_diffs":[{"actual_val":%d,"base_val":%d,"path":"ServiceSettings.ReadTimeout"}]`,
+		fmt.Sprintf(`"config_diffs":[{"actual_val":%d,"base_val":%d,"path":"ServiceSettings.ReadTimeout"}`,
 			timeoutVal+1, timeoutVal))
 }
 

server/channels/api4/metrics_test.go

@@ -30,6 +30,7 @@ func setupMetricsMock() *mocks.MetricsInterface {
 	metricsMock.On("IncrementHTTPError").Return()
 	metricsMock.On("IncrementHTTPRequest").Return()
 	metricsMock.On("ObserveAPIEndpointDuration", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
+	metricsMock.On("ObserveRedisEndpointDuration", mock.AnythingOfType("string"), mock.AnythingOfType("string"), mock.AnythingOfType("float64")).Return()
 	metricsMock.On("Register").Return()
 
 	return metricsMock