Add support for username to redis cache configuration (#7270)

**What this PR does / why we need it**:

Add support for username to redis cache configuration

**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the `CONTRIBUTING.md` guide
- [x] Documentation added
- [ ] Tests updated
- [x] `CHANGELOG.md` updated
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/upgrading/_index.md`

Signed-off-by: Wilfried Roset <wilfriedroset@users.noreply.github.com>

CHANGELOG.md

@@ -22,6 +22,7 @@
 * [5406](https://github.com/grafana/loki/pull/5406) **ctovena**: Revise the configuration parameters that configure the usage report to grafana.com.
 * [7264](https://github.com/grafana/loki/pull/7264) **bboreham**: Chunks: decode varints directly from byte buffer, for speed.
 * [7263](https://github.com/grafana/loki/pull/7263) **bboreham**: Dependencies: klauspost/compress package to v1.15.11; improves performance.
+* [7270](https://github.com/grafana/loki/pull/7270) **wilfriedroset**: Add support for `username` to redis cache configuration.
 
 ##### Fixes
 * [7288](https://github.com/grafana/loki/pull/7288) **ssncferreira**: Fix query mapping in AST mapper `rangemapper` to support the new `VectorExpr` expression.

docs/sources/configuration/_index.md

@@ -1959,6 +1959,10 @@ redis:
   # CLI flag: -<prefix>.redis.pool-size
   [pool_size: <int> | default = 0]
 
+  # Username to use when connecting to redis.
+  # CLI flag: -<prefix>.redis.username
+  [username: <string>]
+
   # Password to use when connecting to redis.
   # CLI flag: -<prefix>.redis.password
   [password: <string>]

pkg/storage/chunk/cache/redis_client.go

@@ -23,6 +23,7 @@ type RedisConfig struct {
 	Expiration         time.Duration  `yaml:"expiration"`
 	DB                 int            `yaml:"db"`
 	PoolSize           int            `yaml:"pool_size"`
+	Username           string         `yaml:"username"`
 	Password           flagext.Secret `yaml:"password"`
 	EnableTLS          bool           `yaml:"tls_enabled"`
 	InsecureSkipVerify bool           `yaml:"tls_insecure_skip_verify"`
@@ -38,6 +39,7 @@ func (cfg *RedisConfig) RegisterFlagsWithPrefix(prefix, description string, f *f
 	f.DurationVar(&cfg.Expiration, prefix+"redis.expiration", 0, description+"How long keys stay in the redis.")
 	f.IntVar(&cfg.DB, prefix+"redis.db", 0, description+"Database index.")
 	f.IntVar(&cfg.PoolSize, prefix+"redis.pool-size", 0, description+"Maximum number of connections in the pool.")
+	f.StringVar(&cfg.Username, prefix+"redis.username", "", description+"Username to use when connecting to redis.")
 	f.Var(&cfg.Password, prefix+"redis.password", description+"Password to use when connecting to redis.")
 	f.BoolVar(&cfg.EnableTLS, prefix+"redis.tls-enabled", false, description+"Enable connecting to redis with TLS.")
 	f.BoolVar(&cfg.InsecureSkipVerify, prefix+"redis.tls-insecure-skip-verify", false, description+"Skip validating server certificate.")
@@ -74,6 +76,7 @@ func NewRedisClient(cfg *RedisConfig) (*RedisClient, error) {
 	opt := &redis.UniversalOptions{
 		Addrs:       endpoints,
 		MasterName:  cfg.MasterName,
+		Username:    cfg.Username,
 		Password:    cfg.Password.String(),
 		DB:          cfg.DB,
 		PoolSize:    cfg.PoolSize,