feat(session): add support for acl-based sentinel auth against redis (#2516)

Implements the sentinel username parameter which can be different to the redis username.

docs/configuration/session/redis.md

@@ -30,6 +30,9 @@ session:
       minimum_version: TLS1.2
     high_availability:
       sentinel_name: mysentinel
+      # If `sentinel_username` is supplied, Authelia will connect using ACL-based
+      # authentication. Otherwise, it will use traditional `requirepass` auth.
+      sentinel_username: sentinel_user
       sentinel_password: sentinel_specific_pass
       nodes:
         - host: sentinel-node1
@@ -148,7 +151,7 @@ required: yes
 The [redis sentinel] master name. This is defined in your [redis sentinel] configuration, it is not a hostname. This
 must be defined currently for a high availability configuration.
 
-#### sentinel_password
+#### sentinel_username
 <div markdown="1">
 type: string
 {: .label .label-config .label-purple }
@@ -156,8 +159,21 @@ required: no
 {: .label .label-config .label-green }
 </div>
 
-The password for the [redis sentinel] connection. A [redis sentinel] username is not supported at this time due to the
-upstream library not supporting it.
+The username for the [redis sentinel] connection. If this is provided, it will be used along with the sentinel_password
+for ACL-based authentication to the Redis Sentinel. If only a password is provided, the [redis sentinel] connection will
+be authenticated with traditional requirepass authentication.
+
+#### sentinel_password
+<div markdown="1">
+type: string
+{: .label .label-config .label-purple }
+required: no (yes if sentinel_username is supplied)
+{: .label .label-config .label-green }
+</div>
+
+The password for the [redis sentinel] connection. If specified with sentinel_username, configures Authelia to
+authenticate to the Redis Sentinel with ACL-based authentication. Otherwise, this is used for requirepass
+authentication.
 
 #### nodes
 

internal/configuration/schema/session.go

@@ -9,6 +9,7 @@ type RedisNode struct {
 // RedisHighAvailabilityConfiguration holds configuration variables for Redis Cluster/Sentinel.
 type RedisHighAvailabilityConfiguration struct {
 	SentinelName     string      `koanf:"sentinel_name"`
+	SentinelUsername string      `koanf:"sentinel_username"`
 	SentinelPassword string      `koanf:"sentinel_password"`
 	Nodes            []RedisNode `koanf:"nodes"`
 	RouteByLatency   bool        `koanf:"route_by_latency"`

internal/session/provider_config.go

@@ -88,6 +88,7 @@ func NewProviderConfig(configuration schema.SessionConfiguration, certPool *x509
 				Logger:           &redisLogger{logger: logging.Logger()},
 				MasterName:       configuration.Redis.HighAvailability.SentinelName,
 				SentinelAddrs:    addrs,
+				SentinelUsername: configuration.Redis.HighAvailability.SentinelUsername,
 				SentinelPassword: configuration.Redis.HighAvailability.SentinelPassword,
 				RouteByLatency:   configuration.Redis.HighAvailability.RouteByLatency,
 				RouteRandomly:    configuration.Redis.HighAvailability.RouteRandomly,