docs(configuration): add redis as session storage

docs/sources/installation/configuration.md

@@ -159,19 +159,19 @@ The database user's password (not applicable for `sqlite3`).
 For Postgres, use either `disable`, `require` or `verify-full`.
 For MySQL, use either `true`, `false`, or `skip-verify`.
 
-### ca_cert_path 
+### ca_cert_path
 
 (MySQL only) The path to the CA certificate to use. On many linux systems, certs can be found in `/etc/ssl/certs`.
 
-### client_key_path 
+### client_key_path
 
 (MySQL only) The path to the client key. Only if server requires client authentication.
 
-### client_cert_path 
+### client_cert_path
 
 (MySQL only) The path to the client cert. Only if server requires client authentication.
 
-### server_cert_name 
+### server_cert_name
 
 (MySQL only) The common name field of the certificate used by the `mysql` server. Not necessary if `ssl_mode` is set to `skip-verify`.
 
@@ -373,7 +373,7 @@ Set to `true` to enable auto sign up of users who do not exist in Grafana DB. De
 
 ### provider
 
-Valid values are `memory`, `file`, `mysql`, `postgres`, `memcache`. Default is `file`.
+Valid values are `memory`, `file`, `mysql`, `postgres`, `memcache` or `redis`. Default is `file`.
 
 ### provider_config
 
@@ -384,6 +384,7 @@ session provider you have configured.
 - **mysql:** go-sql-driver/mysql dsn config string, e.g. `user:password@tcp(127.0.0.1:3306)/database_name`
 - **postgres:** ex:  user=a password=b host=localhost port=5432 dbname=c sslmode=disable
 - **memcache:** ex:  127.0.0.1:11211
+- **redis:** ex: `addr=127.0.0.1:6379,pool_size=100,db=grafana`
 
 If you use MySQL or Postgres as the session store you need to create the
 session table manually.
@@ -415,10 +416,10 @@ How long sessions lasts in seconds. Defaults to `86400` (24 hours).
 
 ### reporting_enabled
 
-When enabled Grafana will send anonymous usage statistics to 
+When enabled Grafana will send anonymous usage statistics to
 `stats.grafana.org`. No IP addresses are being tracked, only simple counters to
 track running instances, versions, dashboard & error counts. It is very helpful
-to us, so please leave this enabled. Counters are sent every 24 hours. Default 
+to us, so please leave this enabled. Counters are sent every 24 hours. Default
 value is `true`.
 
 ### google_analytics_ua_id