feat(sessions): add support for remote redis session store (#3345)

Description
====================
zot currently stores session cookies in memory or in a local directory.
For cases where the session cookies should be independent of the
instance where they were created such as multiple instances of zot, or a
fully stateless zot instance, there is a need to support a remote
session storage.
This change adds support for using Redis and Redis-compatible services as a
remote session driver as well as introduces a new configuration option
for it.

What has changed
=======================
- New config added under Auth config to specify configuration for
  the session driver.
- Examples README updated with details of the new Auth config.
- The config supports only 2 drivers in this change - local and redis
- Using the local driver is backwards compatible and behaves the same
  way that zot currently works for local session storage.
- Omitting this config does not result in an error. In this case, zot
  behaves as it normally does for local session storage.
- When configured, zot can use redis for persisting cookie
  information for zot UI.
- The cookie in the store is deleted on logout or after the max
  expiry time for the cookie.
- Configuration for the redis session driver accepts the same configuration
  values as that of the remote meta cache.
- A separate connection is established for the session driver. An
  existing connection for meta cache will not be re-used for the
  session driver.
- A key prefix is configurable for the redis session driver. The value will be
  converted into a string for use. If no value is provided, a default
  prefix of "zotsession" will be used.
- Redis sessions does not support hash key or encryption in this change.
- New BATS test added to verify zot behavior with Redis session store.
- Github workflow updated to install valkey-tools dependency for BATS.

Signed-off-by: Vishwas Rajashekar <dev@vrajashkr.com>

examples/README.md

@@ -370,6 +370,45 @@ Using that cookie on subsequent calls will authenticate them, asumming the cooki
 In case of using filesystem storage sessions are saved in zot's root directory.
 In case of using cloud storage sessions are saved in memory.
 
+Note: By default, the session driver config would be local for file system or in-memory. The session driver name for this is `local`. An example config is shown below, but the config can be omitted as it is a default.
+
+```
+    "auth": {
+      "htpasswd": {
+        "path": "test/data/htpasswd"
+      },
+      "sessionDriver": {
+        "name": "local"
+      }
+    }
+```
+
+Note: This `sessionDriver` config is optional if a local session storage is desired.
+
+#### Remote Session Storage Driver
+
+Redis and Redis-compatible storage drivers can also be used for cases where session storage is required to be kept separately from zot or multiple zot instances need to share the session information.
+
+This can be configured in the `auth` section of the configuration as shown below:
+
+`sessionDriver`
+
+```
+    "auth": {
+      "htpasswd": {
+        "path": "test/data/htpasswd"
+      },
+      "sessionDriver": {
+        "name": "redis",
+        "url": "redis://localhost:6379",
+        "keyprefix": "zotsession"
+      }
+    }
+```
+
+The `redis` driver configuration options are the same as those in the [Redis Cache Driver](#redis) section. If the `redis` session driver is being used along with a `redis` cache driver and both configurations point to the same Redis instance, there will be two independent connections used.
+
+Note: The `redis` session driver cannot be specified along with configuration for the SessionKeysFile.
 
 ### Securing session based login
 

examples/config-remote-session-store-redis.json

@@ -0,0 +1,34 @@
+{
+  "distSpecVersion": "1.1.1",
+  "storage": {
+    "rootDirectory": "/tmp/zot"
+  },
+  "http": {
+    "address": "127.0.0.1",
+    "port": "8080",
+    "realm": "zot",
+    "auth": {
+      "htpasswd": {
+        "path": "/tmp/zotpasswd"
+      },
+      "sessionDriver": {
+        "name": "redis",
+        "url": "redis://localhost:6379",
+        "keyprefix": "zotsession"
+      }
+    }
+  },
+  "log": {
+    "level": "debug"
+  },
+  "extensions": {
+    "search": {
+      "cve": {
+        "updateInterval": "2h"
+      }
+    },
+    "ui": {
+      "enable": true
+    }
+  }
+}